player: remove unintended !mingw ifdef for IPC uninit

Just wow. This function is implemented in ipc-win.c, and was surely be
meant to be called. But it wasn't called. This could in theory cause
crashes during exit if IPC clients were active.

Untested whether it really works.

player/main.c

@@ -195,10 +195,8 @@ static void shutdown_clients(struct MPContext *mpctx)
 
 void mp_destroy(struct MPContext *mpctx)
 {
-#if !defined(__MINGW32__)
     mp_uninit_ipc(mpctx->ipc_ctx);
     mpctx->ipc_ctx = NULL;
-#endif
 
     shutdown_clients(mpctx);