ci: Compile with Java 11 and run tests with Java 8

Author: lqiu96

.github/workflows/downstream_protobuf_compatibility_check_nightly.yaml

@@ -56,7 +56,6 @@ jobs:
         with:
           java-version: 11
           distribution: temurin
-      - run: echo "JAVA11_HOME=${JAVA_HOME}" >> $GITHUB_ENV
       - name: Print Protobuf-Java testing version
         run: echo "Testing with Protobuf-Java v${{ matrix.protobuf-version }}"
       - name: Perform downstream source compatibility testing

.kokoro/nightly/downstream-protobuf-binary-compatibility.sh

@@ -62,8 +62,6 @@ function build_program_arguments() {
   done
 }
 
-java -version
-
 # TODO(https://github.com/GoogleCloudPlatform/cloud-opensource-java/issues/2395): Java 17+ support for Linkage Checker
 # cloud-opensource-java contains the Linkage Checker tool
 git clone https://github.com/GoogleCloudPlatform/cloud-opensource-java.git

.kokoro/nightly/downstream-protobuf-source-compatibility.sh

@@ -33,7 +33,6 @@ for repo in ${REPOS_UNDER_TEST//,/ }; do # Split on comma
 
   export JAVA_HOME="${JAVA8_HOME}"
   export PATH=$JAVA_HOME/bin:$PATH
-  java -version
 
   # Compile the Handwritten Library with the Protobuf-Java version to test source compatibility
   # Run unit tests to help check for any behavior differences (dependant on coverage)