chore: use RBACTimelock geth wrapper from ccip-owner-contracts (#119)

The timelock-worker repository contained a (incomplete) copy of the geth
wrappers for the RBACTimelock contract. This PR deletes the copy,
replacing it with imports from ccip-owner-contracts repository directly.

(ftr: the ABI and bytecode of the copy matches the one in
ccip-owner-contracts)

Author: gustavogama-cll