fix: Remove colon from step name to fix YAML parsing

The colon in "Fallback: Fetch tags from Azure ACR" was causing
YAML parsing errors in GitHub Actions. Changed to "Fallback Fetch tags..."

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: newbe36524

.github/workflows/azure-to-aliyun-image-sync.yml

@@ -176,7 +176,7 @@ jobs:
           echo "image_versions=${VERSIONS}" >> $GITHUB_OUTPUT
           echo "Versions to sync: ${VERSIONS}"
 
-      - name: Fallback: Fetch tags from Azure ACR
+      - name: Fallback Fetch tags from Azure ACR
         id: fallback-tags
         if: steps.sync-method.outputs.sync_method == 'fallback'
         run: |