Build and Test with java versions 11 & 15

Author: Soroosh Sarabadani

Diff for: .github/workflows/ci.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        java: [8, 11, 15]
+        java: [11, 15]
         kubernetes: ['v1.17.13','v1.18.12','v1.19.4']
     steps:
       - uses: actions/checkout@v2