Make sc_usb_devices_destroy() static

It is only called from the implementation file.

PR #4371 <https://github.com/Genymobile/scrcpy/pull/4371>

Signed-off-by: Romain Vimont <rom@rom1v.com>

app/src/usb/usb.c

@@ -93,7 +93,7 @@ sc_usb_device_move(struct sc_usb_device *dst, struct sc_usb_device *src) {
     src->product = NULL;
 }
 
-void
+static void
 sc_usb_devices_destroy(struct sc_vec_usb_devices *usb_devices) {
     for (size_t i = 0; i < usb_devices->size; ++i) {
         sc_usb_device_destroy(&usb_devices->data[i]);