ci: setup-java sbt cache

https://github.com/actions/setup-java/blob/main/README.md
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f1f9fcd..df3fc9a 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -37,16 +37,6 @@
       with:
         java-version: ${{ matrix.java }}
         distribution: 'zulu'
-    - name: Cache sbt
-      uses: actions/cache@v2
-      with:
-        path: |
-          ~/.sbt
-          ~/.ivy2/cache
-          ~/.coursier/cache/v1
-          ~/.cache/coursier/v1
-          ~/AppData/Local/Coursier/Cache/v1
-          ~/Library/Caches/Coursier/v1
-        key: ${{ runner.os }}-sbt-cache-v2-${{ hashFiles('**/*.sbt') }}-${{ hashFiles('project/build.properties') }}
+        cache: 'sbt'
     - name: Build
       run: sbt ++${{ matrix.scala }} test