Add docs/.* to Zuul jobs irrelevant files list

We don't need to run the CI for changes in the docs
section.

Author: vkmc

zuul.d/projects.yaml

@@ -34,6 +34,7 @@
       - .github/.*
       - ci/github/.*
       - callback_plugins/.*
+      - docs/.*
       - README*
       - OWNERS*
       - .*/*.md