get rid of workflow as it's unused

.github/workflows/gradle.yml

@@ -1,22 +0,0 @@
-name: Java CI
-
-on: [push]
-
-jobs:
-  build:
-
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v1
-    - name: Set up JDK 1.8
-      uses: actions/setup-java@v1
-      with:
-        java-version: 1.8
-    - name: Build with Gradle
-      run: ./gradlew build
-    - name: Upload artifact
-      uses: actions/upload-artifact@v1
-      with:
-        name: KAMI Blue Latest Preview
-        path: /home/runner/work/KAMI/KAMI/build/libs/KAMI-b9-release.jar