Remove duplicated namespace

.github/workflows/docker.yml

@@ -12,7 +12,7 @@ jobs:
     - id: repository
       uses: ASzc/change-string-case-action@v1
       with:
-        string: "${{ github.repository }}/${{ github.event.repository.name }}" 
+        string: "${{ github.repository }}"
     - uses: actions/checkout@v2
     - name: Preparation
       id: prep