Update STATISTICS.md to match code (@ankon, #1936)

Apply the changes from d8b3004:
- "histoor" renamed to "outofrange"
- "mean" removed
- reordered

STATISTICS.md

@@ -118,15 +118,14 @@ avg | int gauge | | Average value
 sum | int gauge | | Sum of values
 cnt | int gauge | | Number of values sampled
 stddev | int gauge | | Standard deviation (based on histogram)
-mean | int gauge | | Mean value (based on histogram)
-histoor | int gauge | | Values skipped due to out of histogram range
 hdrsize | int gauge | | Memory size of Hdr Histogram
 p50 | int gauge | | 50th percentile
 p75 | int gauge | | 75th percentile
 p90 | int gauge | | 90th percentile
 p95 | int gauge | | 95th percentile
 p99 | int gauge | | 99th percentile
 p99_99 | int gauge | | 99.99th percentile
+outofrange | int gauge | | Values skipped due to out of histogram range
 
 
 ## brokers.toppars