Remove workflow

The workflow won't work anymore since Spigot 1.14 is a required dependency.

.github/workflows/maven.yml

@@ -1,26 +0,0 @@
-name: Java CI
-
-on: [push]
-
-jobs:
-  build:
-    runs-on: ubuntu-latest
-
-    steps:
-    - uses: actions/checkout@v2
-    - name: Set up JDK 1.8
-      uses: actions/setup-java@v1
-      with:
-        java-version: 1.8
-    - name: Build with Maven
-      run: mvn package --file pom.xml
-    #- name: Build with Maven and Deploy
-    #  env:
-    #    GITHUB_USERNAME: x-access-token
-    #    GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-    #  run: mvn --settings settings.xml deploy
-    - name: Upload Artifact
-      uses: actions/upload-artifact@v2-preview
-      with:
-        name: Harbor
-        path: target/