Revert "Make OTG window resizable"

On Windows and macOS, resizing blocks the event loop. Handling it
properly would require the same workaround as done in screen.c.

This reverts commit 436b368f9d.

app/src/usb/screen_otg.c

@@ -72,8 +72,7 @@ sc_screen_otg_init(struct sc_screen_otg *screen,
     int width = params->window_width ? params->window_width : 256;
     int height = params->window_height ? params->window_height : 256;
 
-    uint32_t window_flags = SDL_WINDOW_ALLOW_HIGHDPI
+    uint32_t window_flags = SDL_WINDOW_ALLOW_HIGHDPI;
-                          | SDL_WINDOW_RESIZABLE;
     if (params->always_on_top) {
         window_flags |= SDL_WINDOW_ALWAYS_ON_TOP;
     }