kern: Fix a typo in a source code comment

- s/is is/is/

MFC after:	3 days

sys/kern/kern_prot.c

@@ -1761,7 +1761,7 @@ p_candebug(struct thread *td, struct proc *p)
 	if ((p->p_flag & P_INEXEC) != 0)
 		return (EBUSY);
 
-	/* Denied explicitely */
+	/* Denied explicitly */
 	if ((p->p_flag2 & P2_NOTRACE) != 0) {
 		error = priv_check(td, PRIV_DEBUG_DENIED);
 		if (error != 0)

sys/kern/vfs_subr.c

@@ -1565,7 +1565,7 @@ vnlru_proc(void)
 		if (usevnodes <= 0)
 			usevnodes = 1;
 		/*
-		 * The trigger value is is chosen to give a conservatively
+		 * The trigger value is chosen to give a conservatively
 		 * large value to ensure that it alone doesn't prevent
 		 * making progress.  The value can easily be so large that
 		 * it is effectively infinite in some congested and