[SHELL32] Drop slash when dismounting a remote drive. MPR and NP are expecting a drive letter.

This fixes dismounting a network drive using explorer.

dll/win32/shell32/folders/CDrivesFolder.cpp

@@ -253,6 +253,7 @@ HRESULT CALLBACK DrivesContextMenuCallback(IShellFolder *psf,
             else if (wParam == CMDID_DISCONNECT)
             {
                 /* do disconnect */
+                wszBuf[2] = UNICODE_NULL;
                 dwError = WNetCancelConnection2W(wszBuf, 0, FALSE);
                 if (dwError == NO_ERROR)
                 {