nohup: Don't leak fd used to open nohup.out

Since we may redirect stdout, stderr, or both to the file description
referring to the nohup.out file, there is no need to keep the fd that
created that file description around.

Userland/Utilities/nohup.cpp

@@ -44,6 +44,8 @@ void dup_out_file(int fd_to_redirect)
         exit(127);
     }
 
+    MUST(Core::System::close(fd));
+
     if (fd_to_redirect != STDERR_FILENO)
         outln(stderr, "appending output to {}", path);
 }