Fix how-to title grammar

Author: patrikbraborec

sources/platform/actors/development/programming_interface/environment_variables.md

@@ -14,9 +14,9 @@ import TabItem from '@theme/TabItem';
 
 ---
 
-## How to use environment variables in Actors
+## How to use environment variables in an Actor
 
-You can set up environment variables for Actors in two ways:
+You can set up environment variables for your Actor in two ways:
 
 - [Set up environment variables in `actor.json`](#set-up-environment-variables-in-actorjson)
 - [Set up environment variables in Apify Console](#set-up-environment-variables-in-apify-console)