simplify gh action

.github/workflows/maven.yml

@@ -19,11 +19,9 @@ name: GitHub CI
 
 on:
   push:
-    branches:
+    branches-ignore:
-    - master
+      - dependabot/**
   pull_request:
-    branches:
-    - master
 
 jobs:
   build:
@@ -40,20 +38,12 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v2
 
-      - name: Set up cache for ~./m2/repository
-        uses: actions/cache@v2.1.7
-        with:
-          path: ~/.m2/repository
-          key: maven-${{ matrix.os }}-java${{ matrix.java }}-${{ hashFiles('**/pom.xml') }}
-          restore-keys: |
-            maven-${{ matrix.os }}-java${{ matrix.java }}-
-            maven-${{ matrix.os }}-
-
       - name: Set up JDK
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v2.3.1
         with:
           distribution: adopt
           java-version: ${{ matrix.java }}
+          cache: 'maven'
 
       - name: Build with Maven
         run: mvn -e -B -V verify