Publish only on version tags

The previous configuration would run the publish step if the tag matched a version tag, OR if the branch was `master`.

ideally we would run this only if there was a version tag AND the branch was `master`, but this should work for now.

Author: f2prateek

.circleci/config.yml

@@ -31,5 +31,3 @@ workflows:
           filters:
             tags:
               only: /[0-9]+(\.[0-9]+)*(-.+)?/
-            branches:
-              only: master