Remove module needed for wasm workaround for rstest

[keks]

The rstest crate allows using macro attributes other than #[test], but it does require them to have the last element of the module path to be named "test" (e.g. #[foo::test]). However, for wasm it is called wasm_bindgen_test. In order to get rstest to accept it, we have a private module that reexports it using the name test. That way, we can use it in rstest tests.

More context: la10736/rstest#211 (comment)
Private workaround module:

openmls/openmls/src/lib.rs

Lines 194 to 198 in 1412c62

	// this is a workaround, see https://github.com/la10736/rstest/issues/211#issuecomment-1701238125
	#[cfg(any(test, feature = "test-utils"))]
	pub mod wasm {
	pub use wasm_bindgen_test::wasm_bindgen_test as test;
	}

[franziskuskiefer]

We should revisit this together with the custom test framework in the libcrux PR.