Update maven.yml

Author: dengliming

.github/workflows/maven.yml

@@ -9,9 +9,9 @@ jobs:
       matrix:
         java-version: [ 8, 9, 11 ]
     steps:
-    - uses: actions/checkout@v2
-    - uses: actions/setup-java@v1
-      with:
-        java-version: ${{ matrix.java-version }}
-    - name: Build with Maven
-      run: mvn test
+      - uses: actions/checkout@v2
+      - uses: actions/setup-java@v1
+        with:
+          java-version: ${{ matrix.java-version }}
+      - name: Build with Maven
+        run: mvn test