fix(ci): Use a string matcher for the workflow (#1095)

Author: placer14

.circleci/config.yml

@@ -305,7 +305,7 @@ jobs:
 # used in `build-docker-images` workflow below
 branch_filters: &branch_filters
   branches:
-    only: /^cd/staging$/
+    only: cd/staging
   tags:
     ignore: /.*/