btrfs: remove repeated word in struct member comment

Comment for processed extent end of range has an unnecessary "in",
remove it.
Signed-off-by: Nigel Christian <nigel.l.christian@gmail.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -2776,7 +2776,7 @@ struct processed_extent {
 	struct btrfs_inode *inode;
 	/* Start of the range in @inode */
 	u64 start;
-	/* End of the range in in @inode */
+	/* End of the range in @inode */
 	u64 end;
 	bool uptodate;
 };