[AWS] [API Gateway] Fix aggregation types for metrics dashboard

[lucian-ioan]

Urgency

• High

Activity Type

• Bugfix

What does this PR do?

Updates aggregation types in the metrics dashboard for AWS API Gateway to match the statistics used in the integration.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

Author's Checklist

• [ ]

How to test this PR locally

Related issues

• Closes [AWS] [API Gateway] Fix aggregation types for metrics dashboard #7719

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Build stats

• Start Time: 2023-09-06T12:00:14.217+0000

• Duration: 55 min 1 sec

Test stats 🧪

Test	Results
Failed	0
Passed	208
Skipped	4
Total	212

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🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (17/17)	💚
Files	94.444% (17/18)	👎 -5.556
Classes	94.444% (17/18)	👎 -5.556
Methods	85.953% (257/299)	👎 -13.573
Lines	86.024% (7509/8729)	👎 -11.771
Conditionals	100.0% (0/0)	💚

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Package aws - 2.1.2 containing this change is available at https://epr.elastic.co/search?package=aws