nr-uesoftmodem: end with Bye.

Similarly to gNB, eNB, lteUE, end with a "Bye." that the CI (will) check
for.

The right way to do this would be to use the exit code, but most
executables do not actually end with 0, such that we need to check for
this. Thus, this commit is only to harmonize with other executables.

executables/nr-uesoftmodem.c

@@ -500,6 +500,7 @@ int main(int argc, char **argv)
   time_manager_finish();
 
   free(pckg);
+  printf("Bye.\n");
   return 0;
 }