chore(deps): Update Spark dependency to 2.9.4 - running 2.8.0 is no longer supported

Author: deki

.github/workflows/continuous-integration-workflow.yml

@@ -40,8 +40,6 @@ jobs:
       - uses: actions/checkout@v2
       - name: Build latest
         run: ./gha_build.sh spark true true
-      - name: Build Spark 2.8.0
-        run: ./gha_build.sh spark false false -Dspark.version=2.8.0
 
   build_spring:
     name: Build and test Spring & SpringBoot