[docs] fix typo in getting-started

Closes #8354

docs/reference/getting-started.asciidoc

@@ -1029,7 +1029,7 @@ curl -XPOST 'localhost:9200/bank/_search?pretty' -d '
 }'
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-This example demonstrates how we can group by age brackets (ages 20-29, 30-29, and 40-49), then by gender, and then finally get the average account balance, per age bracket, per gender:
+This example demonstrates how we can group by age brackets (ages 20-29, 30-39, and 40-49), then by gender, and then finally get the average account balance, per age bracket, per gender:
 
 [source,sh]
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