aggressive prune_window in cluster-test
aggressive prune_window in cluster-test

setting to 50k versions, so that state pruning kicks in after about 1 min under full load.

Closes: #4814
Approved by: andll

libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,libra/libra,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core