midi2_host: drop unreachable return 0 for IAR Pe111

Same fix as midi2_device — IAR rejects the unreachable statement
after the while(1) superloop. Let int main fall off the end.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

examples/host/midi2_host/src/main.c

@@ -160,6 +160,4 @@ int main(void) {
   while (1) {
     tuh_task();
   }
-
-  return 0;
 }