Removing is_value from types/src/write_set.rs
Removing is_value from types/src/write_set.rs

Unused + untested code

Closes: #1028
Approved by: bothra90

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