Remove redundant warning from feature_request.md (#4065)

Author: vy

.github/ISSUE_TEMPLATE/feature_request.md

@@ -3,7 +3,4 @@ name: Feature request
 about: Submit a feature request
 ---
 
-**Warning!**
-It is highly recommended to discuss feature requests in [the mailing lists](https://logging.apache.org/log4j/2.x/support.html) first.
-
 [A clear and concise description of the feature requested.]