Fix an incorrect error message regarding the size of usize and isize in cast_precision_loss.

[SLUCHABLUB]

When trying to cast a usize or isize using as to a type of potentially smaller size the cast_precision_loss would claim that the size of usize is "32 or 64 bits". It is now corrected to "16, 32, or 64 bits".

changelog: [cast_precision_loss]: fix the error messages claim regarding the size of usize and isize.

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[samueltardieu]

Shouldn't we give a better error message? (and use "may cause" since on 16 bit usize platforms this is fine)

For example:

casting `usize` to `f32` may cause a loss of precision (`usize` can be as large as 64 bits wide depending of the target architecture, but `f32`'s mantissa is only 23 bits wide)

[SLUCHABLUB]

Yes, something like that would be even better. I will look over it.

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