relayer tx simulation call does not work on mainnet
See the following logs:
```
2023-04-25T19:06:44.045Z	DEBUG	relayer	relayer/submit_transaction.go:81	relaying tx with gas price 47898010734
2023-04-25T19:06:44.091Z	ERROR	relayer	relayer/submit_transaction.go:93	failed to simulate execute: err: insufficient funds for gas * price + value: address 0x9017f022AE58452949f092363505B0196142eC3b have 48333473886691647 want 26343905903700000000 (supplied gas 550000000)
2023-04-25T19:06:44.091Z	DEBUG	net	net/relay.go:82	did not handle relay request: err: insufficient funds for gas * price + value: address 0x9017f022AE58452949f092363505B0196142eC3b have 48333473886691647 want 26343905903700000000 (supplied gas 550000000)
```

I suspect it's due to the `txOpts.GasLimit` not being set (notice the log above is setting the gas limit to 550000000) :/ 