Update Gradle to 7.0, other stuff

.github/workflows/build.yml

@@ -14,7 +14,7 @@ jobs:
         java: [
           1.8,  # Minimum supported by Minecraft
           11,   # Current Java LTS
-          15    # Latest version
+          16    # Latest version
         ]
         # and run on both Linux and Windows
         os: [ubuntu-20.04, windows-latest]
@@ -25,8 +25,9 @@ jobs:
       - name: validate gradle wrapper
         uses: gradle/wrapper-validation-action@v1
       - name: setup jdk ${{ matrix.java }}
-        uses: actions/setup-java@v1
+        uses: actions/setup-java@v2
         with:
+          distribution: zulu
           java-version: ${{ matrix.java }}
       - name: make gradle wrapper executable
         if: ${{ runner.os != 'Windows' }}