Fix circleci publish_latest_horizon_docker_image job (#2049)

Because CircleCI does not build tags by default, any child jobs that rely on a job that only builds on tags will also require the tag filter. In this case, the hold and publish_latest_horizon_docker_image jobs will need the filter for /^horizon-v.*/ tags as well, otherwise, they will not be picked up for running.

.circleci/config.yml

@@ -328,10 +328,20 @@ workflows:
               branches:
                 ignore: /.*/
       - hold: # <<< A job that will require manual approval in the CircleCI web application.
+          filters:
+              tags:
+                only: /^horizon-v.*/
+              branches:
+                ignore: /.*/
           type: approval # <<< This key-value pair will set your workflow to a status of "On Hold"
           requires: # We only run the "hold" job when publish_horizon_docker_image has succeeded
            - publish_horizon_docker_image
-      # Pushing stellar/horizon:latest to docker hub requires manual approval
       - publish_latest_horizon_docker_image:
+          filters:
+              tags:
+                only: /^horizon-v.*/
+              branches:
+                ignore: /.*/
+          # Pushing stellar/horizon:latest to docker hub requires manual approval
           requires:
             - hold