fix: dashboard image push condition (#385)

diff --git a/.github/workflows/dashboard_push_docker_hub.yaml b/.github/workflows/dashboard_push_docker_hub.yaml
index 73c6e51..c21c5d7 100644
--- a/.github/workflows/dashboard_push_docker_hub.yaml
+++ b/.github/workflows/dashboard_push_docker_hub.yaml
@@ -5,11 +5,11 @@
 jobs:
   build:
     strategy:
-        fail-fast: false
-        matrix:
-          os:
-            - centos
-            - alpine
+      fail-fast: false
+      matrix:
+        os:
+          - centos
+          - alpine
 
     name: build dashboard & test on ${{ matrix.os }} && push to docker hub
     runs-on: ubuntu-latest
@@ -56,6 +56,6 @@
         uses: docker/setup-buildx-action@v1
 
       - name: Push apisix dashboard image to Docker Hub
-        if: matrix.platform == 'centos'
+        if: matrix.os == 'centos'
         run: |
           make push-multiarch-dashboard