Update revision of commit-message-length-plugin

- Use "warning" prefix to allow colorization of remote output

Change-Id: Ic968dc5e894ae95f70f0e2b321745190b9c1093e
diff --git a/plugins/commit-message-length-validator b/plugins/commit-message-length-validator
index 315a115..4f6b685 160000
--- a/plugins/commit-message-length-validator
+++ b/plugins/commit-message-length-validator
@@ -1 +1 @@
-Subproject commit 315a11558913fa8f9c6d3b1723e45583b25afa1c
+Subproject commit 4f6b685e12e34a4f583cf84ba1c58ccc2b75e8b0