Remove master from code-freeze and fix release branch regex (#3715)

Signed-off-by: Andrew Leonard <anleonar@redhat.com>

.github/workflows/code-freeze.yml

@@ -3,7 +3,7 @@ name: Code Freeze Bot
 # Controls when the workflow will run
 on:
   pull_request_target:
-    branches: [ "master", "v[0-9]{4}.[0-9]{2}.[0-9]{2}" ]
+    branches: [ "v[0-9]+.[0-9]+.[0-9]+" ]
   issue_comment:
     types: [created]