Remove gradle-wrapper.jar from source

Now that we use git export to produce the source release, there is gradle-wrapper binary jar file in https://github.com/apache/solr/tree/main/gradle/wrapper that we are not allowed to include legally (LEGAL-570). Comparing with lucene, they do not have the jar file in git and thus not in the source release either.

So I believe the solution is to remove the jar from Solr's git and let "gradlew" script download it for you...

At first I hacked the smoketester to allow this one jar file, but that was wrong, will revert that change...