docker: dont login when in PR (#5961)

.github/workflows/docker.yml

@@ -14,12 +14,6 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-<<<<<<< HEAD
-      - uses: actions/setup-go@v2
-        with:
-          go-version: "^1.15.4"
-=======
->>>>>>> cd3ebe875... docker: release Linux/ARM64 image (#5925)
       - uses: actions/checkout@master
       - name: Prepare
         id: prep
@@ -49,6 +43,7 @@ jobs:
         uses: docker/setup-buildx-action@v1
 
       - name: Login to DockerHub
+        if: ${{ github.event_name != 'pull_request' }}
         uses: docker/login-action@v1
         with:
           username: ${{ secrets.DOCKERHUB_USERNAME }}