src: Windows: remove useless transmute

This fixes following clippy warning:

	Error:    --> src\lib.rs:605:31
	    |
	605 |         let handle = unsafe { mem::transmute(handle) };
	    |                               ^^^^^^^^^^^^^^^^^^^^^^
	    |
	    = note: `-D clippy::useless-transmute` implied by `-D warnings`
	    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#useless_transmute

Signed-off-by: Richard Leitner <dev@g0hl1n.net>

src/lib.rs

@@ -602,7 +602,6 @@ impl TryFrom<NativeBlockingSerialPort> for SerialStream {
             log::error!("unable to open new async file handle");
             return Err(crate::Error::from(StdIoError::last_os_error()));
         }
-        let handle = unsafe { mem::transmute(handle) };
 
         // Construct NamedPipe and COMPort from Handle
         //