Revert "docs: update README options version from required to optional (golangci#1145)"

This reverts commit e087933.

Author: baburciu

README.md

@@ -257,7 +257,7 @@ You will also likely need to add the following `.gitattributes` file to ensure t
 
 ### `version`
 
-(optional)
+(required)
 
 The version of golangci-lint to use.