ci: use native gh actions gradle cache

.github/workflows/ci.yml

@@ -3,25 +3,20 @@ name: CI
 on:
   push:
     branches:
-      - master
+      - main
   pull_request:
 
 jobs:
   build:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v2
+
       - uses: actions/setup-java@v3
         with:
           java-version: 17
           distribution: adopt
-      - uses: actions/cache@v2
-        with:
-          path: |
-            ~/.gradle/caches
-            ~/.gradle/wrapper
-          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*') }}
-          restore-keys: |
-            ${{ runner.os }}-gradle-
-      - name: Build the theme
+          cache: 'gradle'
+
+      - name: 🧱 Build the theme
         run: make