Fixing typos in JSON field names

[ycombinator]

What does this PR do?

Fix typos introduced in #16538.

Why is it important?

So the correct field names are used when indexing type: index_stats data into .monitoring-es-* indices.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works

[elasticmachine]

Pinging @elastic/stack-monitoring (Stack monitoring)

[elasticmachine]

Pinging @elastic/integrations-services (Team:Services)

[chrisronline]

LGTM!

{
  "hits": {
    "hits": [
      {
        "_source": {
          "index_stats": {
            "total": {
              "search": {
                "query_total": 398,
                "query_time_in_millis": 432
              },
              "fielddata": {
                "memory_size_in_bytes": 1344,
                "evictions": 0
              },
              "indexing": {
                "index_total": 374,
                "index_time_in_millis": 404,
                "throttle_time_in_millis": 0
              },
              "store": {
                "size_in_bytes": 443322
              },
              "refresh": {
                "external_total_time_in_millis": 3846,
                "total_time_in_millis": 3663
              },
              "segments": {
                "terms_memory_in_bytes": 67840,
                "index_writer_memory_in_bytes": 0,
                "count": 10,
                "norms_memory_in_bytes": 0,
                "version_map_memory_in_bytes": 0,
                "term_vectors_memory_in_bytes": 0,
                "points_memory_in_bytes": 0,
                "stored_fields_memory_in_bytes": 4944,
                "memory_in_bytes": 107352,
                "doc_values_memory_in_bytes": 34568,
                "fixed_bit_set_memory_in_bytes": 0
              },
              "docs": {
                "count": 374
              },
              "request_cache": {
                "evictions": 0,
                "hit_count": 15,
                "miss_count": 251,
                "memory_size_in_bytes": 7330
              },
              "merges": {
                "total_size_in_bytes": 6152784
              },
              "query_cache": {
                "hit_count": 0,
                "miss_count": 0,
                "memory_size_in_bytes": 0,
                "evictions": 0
              }
            },
            "uuid": "MIuBVme_QBiadsCw3e2rVw",
            "index": ".monitoring-beats-7-mb-2020.03.18",
            "created": 1584545718254,
            "status": "green",
            "shards": {
              "unassigned_total": 0,
              "total": 1,
              "replicas": 0,
              "active_total": 1,
              "active_primaries": 1,
              "initializing": 0,
              "relocating": 0,
              "unassigned_replicas": 0,
              "active_replicas": 0,
              "unassigned_primaries": 0,
              "primaries": 1
            },
            "primaries": {
              "store": {
                "size_in_bytes": 443322
              },
              "query_cache": {
                "miss_count": 0,
                "memory_size_in_bytes": 0,
                "evictions": 0,
                "hit_count": 0
              },
              "docs": {
                "count": 374
              },
              "indexing": {
                "index_total": 374,
                "index_time_in_millis": 404,
                "throttle_time_in_millis": 0
              },
              "search": {
                "query_time_in_millis": 432,
                "query_total": 398
              },
              "fielddata": {
                "memory_size_in_bytes": 1344,
                "evictions": 0
              },
              "request_cache": {
                "hit_count": 15,
                "miss_count": 251,
                "memory_size_in_bytes": 7330,
                "evictions": 0
              },
              "segments": {
                "fixed_bit_set_memory_in_bytes": 0,
                "version_map_memory_in_bytes": 0,
                "memory_in_bytes": 107352,
                "index_writer_memory_in_bytes": 0,
                "stored_fields_memory_in_bytes": 4944,
                "term_vectors_memory_in_bytes": 0,
                "points_memory_in_bytes": 0,
                "count": 10,
                "terms_memory_in_bytes": 67840,
                "norms_memory_in_bytes": 0,
                "doc_values_memory_in_bytes": 34568
              },
              "refresh": {
                "external_total_time_in_millis": 3846,
                "total_time_in_millis": 3663
              },
              "merges": {
                "total_size_in_bytes": 6152784
              }
            }
          }
        }
      }
    ]
  }
}

[ycombinator]

Travis CI is green and Jenkins CI failures are unrelated. Merging.