btrfs: send: fix grammar in comments

Fix a few obvious grammar mistakes: a -> an, then -> than.

Signed-off-by: Thorsten Blum <[e-mail]>
Reviewed-by: David Sterba <[e-mail]>
Signed-off-by: David Sterba <[e-mail]>

fs/btrfs/send.c

···
 		/*
 		 * Average path length does not exceed 200 bytes, we'll have
 		 * better packing in the slab and higher chance to satisfy
-		 * a allocation later during send.
+		 * an allocation later during send.
 		 */
 		char pad[256];
 	};
···
 	/*
 	 * Start with a small buffer (1 page). If later we end up needing more
 	 * space, which can happen for xattrs on a fs with a leaf size greater
-	 * then the page size, attempt to increase the buffer. Typically xattr
+	 * than the page size, attempt to increase the buffer. Typically xattr
 	 * values are small.
 	 */
 	buf_len = PATH_MAX;