Remove stale comment. splhigh -> critical_enter transition happend

some time ago, and no longer needs special attention.

sys/mips/mips/pmap.c

@@ -1192,12 +1192,6 @@ pmap_release(pmap_t pmap)
 	vm_page_unlock_queues();
 }
 
-/*
- * Changes:
- *	 * Replace splhigh()/splx() with critical_enter()/critical_exit()
- *	 * Use the VM_ALLOC_WIRED flag for allocating the new page.
- */
-
 /*
  * grow the number of kernel page table entries, if needed
  */