feat(wasm): Fix cargo runtime on Wasm platforms (#5220)

When file was
[moved](2a14077)
it looks like an update was missed, since wasm is not in the CI yet.

Signed-off-by: Daniel Salinas

Author: zzorba

bindings/matrix-sdk-ffi/src/runtime.rs

@@ -39,7 +39,7 @@ mod sys {
 mod sys {
     use std::future::Future;
 
-    use crate::executor::{spawn, JoinHandle};
+    use matrix_sdk_common::executor::{spawn, JoinHandle};
 
     /// A dummy guard that does nothing when dropped.
     /// This is used for the Wasm implementation to match