Documentation: git-add does not update files marked "assume unchanged"

Signed-off-by: Clemens Buchacher <drizzd@aon.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-update-index.txt

@@ -93,8 +93,6 @@ OPTIONS
 This option can be also used as a coarse file-level mechanism
 to ignore uncommitted changes in tracked files (akin to what
 `.gitignore` does for untracked files).
-You should remember that an explicit 'git add' operation will
-still cause the file to be refreshed from the working tree.
 Git will fail (gracefully) in case it needs to modify this file
 in the index e.g. when merging in a commit;
 thus, in case the assumed-untracked file is changed upstream,