use github.ref_name for tag name

Signed-off-by: Trevor James Smith <10819524+Zeitsperre@users.noreply.github.com>

Author: Zeitsperre

.github/workflows/tests.yml

@@ -170,4 +170,4 @@ jobs:
         with:
           file: "Dockerfile"
           push: true
-          tags: birdhouse/twitcher:latest,birdhouse/twitcher:${{ GITHUB_REF##*/ }}
+          tags: birdhouse/twitcher:latest,birdhouse/twitcher:${{ github.ref_name }}