Remove last traces of ->sync_page

Commit 7eaceaccab removed ->sync_page, but a few mentions of it still
existed in documentation and comments,

Signed-off-by: Matthew Wilcox <matthew.r.wilcox@intel.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/isofs/compress.c

@@ -361,7 +361,6 @@ static int zisofs_readpage(struct file *file, struct page *page)
 
 const struct address_space_operations zisofs_aops = {
 	.readpage = zisofs_readpage,
-	/* No sync_page operation supported? */
 	/* No bmap operation supported */
 };