Fix typo in docs

docs/reference/aggregations/bucket/histogram-aggregation.asciidoc

@@ -18,7 +18,7 @@ if (rem < 0) {
 bucket_key = value - rem
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-From the rounding function above it can be seen that the intervals themsevles **must** be integers.
+From the rounding function above it can be seen that the intervals themselves **must** be integers.
 
 The following snippet "buckets" the products based on their `price` by interval of `50`: