Use Gradle wrapper in client benchmark README
Use Gradle wrapper in client benchmark README

With this commit we use the Gradle wrapper in documentation examples for the
client benchmarks instead of Gradle itself.

Relates #35366
scorpionvicky/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,robin13/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,coding0011/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,nknize/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,GlenRSmith/elasticsearch,GlenRSmith/elasticsearch,HonzaKral/elasticsearch,robin13/elasticsearch,robin13/elasticsearch,uschindler/elasticsearch,scorpionvicky/elasticsearch,nknize/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,coding0011/elasticsearch,scorpionvicky/elasticsearch,coding0011/elasticsearch,gingerwizard/elasticsearch,GlenRSmith/elasticsearch,gingerwizard/elasticsearch,scorpionvicky/elasticsearch,gingerwizard/elasticsearch,HonzaKral/elasticsearch,nknize/elasticsearch,uschindler/elasticsearch,HonzaKral/elasticsearch,gingerwizard/elasticsearch,coding0011/elasticsearch,uschindler/elasticsearch