Update environment_variables.md (#1266)

Author: jancurn

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

@@ -5,9 +5,9 @@ slug: /actors/development/programming-interface/environment-variables
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-# Environment variables in Apify
+# Actor environment variables
 
-**Learn how to provide your Actor with context that determines its behavior through a plethora of pre-defined environment variables offered by the Apify SDK.**
+**Learn how to provide your Actor with context that determines its behavior through a plethora of pre-defined environment variables set by the Apify platform.**
 
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