Removing export_counter from common/metrics/src/lib.rs
Removing export_counter from common/metrics/src/lib.rs

Closes: #4219
Approved by: bmwill

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