Remove getMaterial3ThemeAsync()

[Aimarekin]

getMaterial3ThemeAsync() is a promise-wrapped version of getMaterial3Theme() which is otherwise functionally identical. The Kotlin module definition also just defines getSystemThemeAsync as identical to getSystemTheme.

Seeing at the code's history, I haven't found a reason to be for these async functions. Commit d32fe22 seems to have introduced it, exactly as it is now. Perhaps it was a mistake?

[pchmn]

AsyncFunction in expo modules are used to run js functions on different thread than the main one : https://docs.expo.dev/modules/module-api/#asyncfunction

So it's not really just a promise-wrapped version of getMaterial3Theme().

I should put some doc on it

[Aimarekin]

@pchmn Oh alright, I didn't know about that - thanks. Some docs would be nice!