[DOCS] Add caveat for the priority fee

[sbvegan]

Brief Description of the Docs Request

There is a slight caveat for the minimum priority fee.

Description of the Documentation You'd Like

Update the following statement with the nuance from the quotes in the additional context.

The priority fee is an optional component of the execution gas fee and can be set to 0.

Links to Related Pages

https://docs.optimism.io/stack/transactions/fees

Additional Context

EIP-1559 doesn't specify a minimum priority fee, so zero should be ok. But wallets and mempools (Geth, as mentioned) sometimes impose a minimum for who knows what reason.

I think geth hardcodes a minimum fee of 1 wei. Then it also has a configurable value which defaults to like 1 GWEI.