lockfile: fix documentation on close_lock_file_gently()

Commit 83a3069 (lockfile: do not rollback lock on failed close,
2017-09-05) forgot to update the documentation by the function definition
to reflect that the lock is not rolled back in case closing fails.

Signed-off-by: Martin Ågren <martin.agren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

lockfile.h

@@ -240,8 +240,8 @@ extern char *get_locked_file_path(struct lock_file *lk);
  * If the lockfile is still open, close it (and the file pointer if it
  * has been opened using `fdopen_lock_file()`) without renaming the
  * lockfile over the file being locked. Return 0 upon success. On
- * failure to `close(2)`, return a negative value and roll back the
- * lock file. Usually `commit_lock_file()`, `commit_lock_file_to()`,
+ * failure to `close(2)`, return a negative value (the lockfile is not
+ * rolled back). Usually `commit_lock_file()`, `commit_lock_file_to()`,
  * or `rollback_lock_file()` should eventually be called.
  */
 static inline int close_lock_file_gently(struct lock_file *lk)