fix: add exclusion for main tags in cleanup workflow

Author: n3rdc4ptn

.github/workflows/clean-main-images.yml

@@ -32,3 +32,4 @@ jobs:
           keep-n-tagged: ${{ env.KEEP_X_IMAGES }}
           delete-ghost-images: true
           delete-partial-images: true
+          exclude-tags: "main"