crypto: Don't manually implement Send, those are now in olm-rs.

src/crypto/olm.rs

@@ -46,14 +46,6 @@ impl fmt::Debug for Account {
     }
 }
 
-/// Marking this as Send is safe because nothing will modify the pointer under
-/// us from the C side. Sync on the other hand is unsafe since libolm doesn't do
-/// any synchronization. We're wrapping the whole Olm machine inside a Mutex to
-/// get Sync for it
-unsafe impl Send for Account {}
-unsafe impl Send for Session {}
-unsafe impl Send for InboundGroupSession {}
-
 impl Account {
     /// Create a new account.
     pub fn new() -> Self {