docs: add note back about large toml numbers

[mattsse]

Motivation

add note back removed in #918

Solution

[onbjerg]

So this effectively means that you can only lower the gas limit?

[mattsse]

So this effectively means that you can only lower the gas limit?

only wanted to insert the comment not update the value...

[onbjerg]

Oh, right, I also misunderstood something

[onbjerg]

Wait, no, I'm right: The max value for a u64 is 18446744073709551615 - our default is half of that, which is 9223372036854775807, which also happens to be the max value of an i64. So you can effectively only lower the gas limit because of this bug :S

[mattsse]

perhaps I can find a solution with a custom wrapper type

[onbjerg]

Can just merge this since it's a comment and then we fix it later