Revert "YARN-6022. Document Docker work as experimental (Contributed by Varun Vasudev)"

This reverts commit 66be6c848b47ae7248b0658e3bb2149d2387cebd.

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-site/src/site/markdown/DockerContainers.md

@@ -17,12 +17,6 @@ Launching Applications Using Docker Containers
 
 <!-- MACRO{toc|fromDepth=0|toDepth=1} -->
 
-Notice
-------
-This feature is experimental and is not complete. Enabling this feature and
-running Docker containers in your cluster has security implications.
-Please do a security analysis before enabling this feature.
-
 Overview
 --------