Update CONTRIBUTING.md to indicate Gradle >= 4.3 is required (#27980)
Update CONTRIBUTING.md to indicate Gradle >= 4.3 is required (#27980)

Relates #27885.
vroyer/elassandra,vroyer/elassandra,vroyer/elasticassandra,vroyer/elassandra,strapdata/elassandra,vroyer/elasticassandra,strapdata/elassandra,strapdata/elassandra,vroyer/elasticassandra,strapdata/elassandra,strapdata/elassandra