Make the ext-types proc-macro tests pass again

This started failing because of #1809.  I don't think that's a new
issue, but somehow the changes in this branch caused the tests to start
failing.

Removing this extra function, which I didn't mean to commit in the first
place, makes the tests pass.  Let's fix it for real in another branch.

fixtures/ext-types/uniffi-one/src/lib.rs

@@ -34,9 +34,4 @@ fn get_my_proc_macro_type(t: UniffiOneProcMacroType) -> UniffiOneProcMacroType {
     t
 }
 
-#[uniffi::export]
-async fn get_uniffi_one_async() -> UniffiOneEnum {
-    UniffiOneEnum::One
-}
-
 uniffi::include_scaffolding!("uniffi-one");