Simulation ignores gas limits

[schmanu]

Bug description

If a transaction is fully signed or only the current owner's signature is missing we do not need and should not overwrite the safe's threshold and pass the manual selected or estimated gas limit.

Reason: The number of signatures matters for the transactions gas limit. If the tx will only check 1 signature instead of n>1 signatures it can occur that a successfully simulated tx reverts when being executed.

Steps to reproduce

1. Create a new ERC20 transfer
2. Go to review step
3. change the gas limit to 21000 (minimum)
4. click simulate
5. Observe simulation success
6. try to execute with that gas limit
7. Observe error: Your transaction was unsuccessful. [ethjs-query] while formatting outputs from RPC '{"value":{"code":-32000,"message":"intrinsic gas too low"}}'

Expected result

The simulation should fail with "out of gas"

Obtained result

The simulation always uses 30 million gas as limit and always succeeds.