Minor fix for java benchmark script, as grep does not support -P option.

frameworks/Kieker-java/benchmark.sh

@@ -11,8 +11,8 @@ MAIN_DIR="${BASE_DIR}/../.."
 
 # Hotfix for ASPECTJ
 # https://stackoverflow.com/questions/70411097/instrument-java-17-with-aspectj
-JAVA_VERSION=$(java -version 2>&1 | grep -oP 'version "?(1\.)?\K\d+')
-if [ "$JAVA_VERSION" != "8" ]
+JAVA_VERSION=$(java -version 2>&1 | grep -o 'version "[0-9]*' | sed 's/.*"\([0-9]*\)/\1/g')
+if [ "${JAVA_VERSION}" != "8" ]
 then
 	export JAVA_OPTS="--add-opens java.base/java.lang=ALL-UNNAMED"
 	echo "Setting \$JAVA_OPTS, since Java version is bigger than 8"