kernel: remove reference to feature-removal-schedule.txt

In commit 9c0ece069b32 ("Get rid of Documentation/feature-removal.txt"),
Linus removed feature-removal-schedule.txt from Documentation, but there
is still some reference to this file. So remove them.

Signed-off-by: Tao Ma <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

kernel/cgroup.c

···
 	if (ret)
 		goto out_unlock;
 
-	/* See feature-removal-schedule.txt */
 	if (opts.subsys_mask != root->actual_subsys_mask || opts.release_agent)
 		pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
 			   task_tgid_nr(current), current->comm);

kernel/module.c

···
 			printk(KERN_WARNING "Symbol %s is being used "
 			       "by a non-GPL module, which will not "
 			       "be allowed in the future\n", fsa->name);
-			printk(KERN_WARNING "Please see the file "
-			       "Documentation/feature-removal-schedule.txt "
-			       "in the kernel source tree for more details.\n");
 		}
 	}