docs: fix CHANGELOG.md

Co-authored-by: Pavel Závora <[email protected]>

Author: bednar

CHANGELOG.md

@@ -1,7 +1,7 @@
 ## 1.22.0 [unreleased]
 
 ### Features
-1. [#335](https://github.com/influxdata/influxdb-client-python/pull/335): Add supports for custom precision for index specified as number [DataFrame] 
+1. [#335](https://github.com/influxdata/influxdb-client-python/pull/335): Add support for custom precision for index specified as a number [DataFrame] 
 
 ## 1.21.0 [2021-09-17]