[Core] Minor: measure text function taking a pointer is redundant

[mikejsavage]

Clay's text measuring callback is defined to take a pointer to Clay_String, which seems redundant because Clay_String is already a pointer.

I may be wrong but it looks like the rest of the codebase takes Clay_String directly, besides some things that are downstream of MeasureText.

[nicbarker]

Yes, I'd say you're probably right. It will be a breaking change at this point though, so I'll have to do it soon if it were to change 😅

[Muzz]

Imo it's a new library, you should just make breaking changes for the first few versions, and focus on nailing all this stuff in the short term.