writeback: fix typo in comment

Spelling mistake (triple letters) in comment.
Detected with the help of Coccinelle.

Link: https://lore.kernel.org/r/20220521111145.81697-32-Julia.Lawall@inria.frSigned-off-by: Julia Lawall <Julia.Lawall@inria.fr>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/fs-writeback.c

@@ -738,7 +738,7 @@ EXPORT_SYMBOL_GPL(wbc_attach_and_unlock_inode);
  * incorrectly attributed).
  *
  * To resolve this issue, cgroup writeback detects the majority dirtier of
- * an inode and transfers the ownership to it.  To avoid unnnecessary
+ * an inode and transfers the ownership to it.  To avoid unnecessary
  * oscillation, the detection mechanism keeps track of history and gives
  * out the switch verdict only if the foreign usage pattern is stable over
  * a certain amount of time and/or writeback attempts.