read-cache-ll: fix a typo

Fix a typo in comments.

Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Author: algonell

read-cache-ll.h

@@ -151,7 +151,7 @@ enum sparse_index_mode {
 
 	/*
 	 * The index has already been collapsed to sparse directories
-	 * whereever possible.
+	 * wherever possible.
 	 */
 	INDEX_COLLAPSED,