remove outdated comments from filemap.c

@@ -29,11 +29,6 @@
 #include <linux/security.h>
 #include <linux/syscalls.h>
 /*
- * This is needed for the following functions:
- *  - try_to_release_page
- *  - block_invalidatepage
- *  - generic_osync_inode
- *
  * FIXME: remove all knowledge of the buffer layer from the core VM
  */
 #include <linux/buffer_head.h> /* for generic_osync_inode */