Simplifying linkage monitor test setup (#6855)

tests.sh

@@ -251,16 +251,6 @@ build_java_linkage_monitor() {
   # Linkage Monitor uses $HOME/.m2 local repository
   MVN="mvn -e -B -Dhttps.protocols=TLSv1.2"
   cd java
-  # Sets java artifact version with SNAPSHOT, as Linkage Monitor looks for SNAPSHOT versions.
-  # Example: "3.9.0" (without 'rc')
-  VERSION=`grep '<version>' pom.xml |head -1 |perl -nle 'print $1 if m/<version>(\d+\.\d+.\d+)/'`
-  cd bom
-  # This local installation avoids the problem caused by a new version not yet in Maven Central
-  # https://github.com/protocolbuffers/protobuf/issues/6627
-  $MVN install
-  $MVN versions:set -DnewVersion=${VERSION}-SNAPSHOT
-  cd ..
-  $MVN versions:set -DnewVersion=${VERSION}-SNAPSHOT
   # Installs the snapshot version locally
   $MVN install -Dmaven.test.skip=true