update github actions

now runs at every push or pull request regardless of branch
and runs once a month to check that compiling still works
also now runs latest java 8 for testing

.github/workflows/gradle.yml

@@ -5,9 +5,9 @@ name: Check code
 
 on:
   push:
-    branches: [ 1.7.10 ]
   pull_request:
-    branches: [ 1.7.10 ]
+  schedule:
+    - cron: '0 12 1 * *'
 
 jobs:
   build:
@@ -19,7 +19,7 @@ jobs:
     - name: Set up JDK 8
       uses: actions/setup-java@v2
       with:
-        java-version: '8.0.292+10'
+        java-version: '8'
         distribution: 'adopt'
     - name: Grant execute permission for gradlew
       run: chmod +x gradlew