ext4: fix comments in ext4_can_extents_be_merged()

Since commit a9b8241594add, we are allowed to merge unwritten extents,
so here these comments are wrong, remove it.

Signed-off-by: Xiaoguang Wang <wangxg.fnst@cn.fujitsu.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/extents.c

@@ -1717,12 +1717,6 @@ ext4_can_extents_be_merged(struct inode *inode, struct ext4_extent *ex1,
 {
 	unsigned short ext1_ee_len, ext2_ee_len;
 
-	/*
-	 * Make sure that both extents are initialized. We don't merge
-	 * unwritten extents so that we can be sure that end_io code has
-	 * the extent that was written properly split out and conversion to
-	 * initialized is trivial.
-	 */
 	if (ext4_ext_is_unwritten(ex1) != ext4_ext_is_unwritten(ex2))
 		return 0;