Update required Java version for GitHub CI

Change-Id: I6bdab1f3a8e0e73b86bfb6a16ca2dca4c177ebd0
diff --git a/.github/workflows/ci_test_and_coverage.yml b/.github/workflows/ci_test_and_coverage.yml
index 346e3f1..a756e96 100644
--- a/.github/workflows/ci_test_and_coverage.yml
+++ b/.github/workflows/ci_test_and_coverage.yml
@@ -9,10 +9,10 @@
       - name: Checkout Krill
         uses: actions/checkout@v2
 
-      - name: Set up JDK 1.8
+      - name: Set up JDK 11
         uses: actions/setup-java@v1
         with:
-          java-version: 1.8
+          java-version: 11
 
       - name: Build and install Krill
         run: mvn install