Deploy to firebase on docs_deploy test.

Docs deploy post processing the api docs bundle correctly but it was only
uploading to firebase for master|main branch. This change also uploads
to firebase if the branch is stable.

Change-Id: I6dd8df9a5a551e136ba6866d92694bf89c93622a
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/35040
Reviewed-by: Casey Hillers <chillers@google.com>
Commit-Queue: Godofredo Contreras <godofredoc@google.com>

recipe_modules/adhoc_validation/api.py

diff --git a/recipe_modules/adhoc_validation/api.py b/recipe_modules/adhoc_validation/api.py
index 046c6cc..fd0869c 100644
--- a/recipe_modules/adhoc_validation/api.py
+++ b/recipe_modules/adhoc_validation/api.py
@@ -76,7 +76,8 @@
               self.m.bucket_util.upload_folder('Upload API Docs', docs_path, 'doc', "api_docs.zip")
             project = self.m.properties.get('firebase_project')
             # Only deploy to firebase directly if this is master or main.
-            if (self.m.properties.get('git_branch') in ['master', 'main']):
+            if ((self.m.properties.get('git_branch') in ['master', 'main']) or
+                (self.m.properties.get('release_ref') == 'refs/heads/stable')):
               self.m.firebase.deploy_docs(
                   env=env,
                   env_prefixes=env_prefixes,