Update workflow

.github/workflows/gradle.yml

@@ -3,19 +3,20 @@ name: Java CI
 on:
   push:
     branches:
-    - 1.15
+    - '1.15'
   pull_request:
     branches:
-    - 1.15
+    - '1.15'
  
 jobs:
   test:
     runs-on: ubuntu-18.04
 
     steps:
-    - uses: actions/checkout@v1
-    - name: Set up JDK 1.8
-      uses: actions/setup-java@v1
+    - name: Checkout
+      uses: actions/checkout@v2.0.0
+    - name: Setup Java JDK
+      uses: actions/setup-java@v1.3.0
       with:
         java-version: 1.8
     - name: Download BuildTools