Documentation: fix a typo in git-apply.txt

git-apply accepts the --cached option, not --cache.
Signed-off-by: NMichał Kiedrowicz <michal.kiedrowicz@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/git-apply.txt

@@ -22,7 +22,7 @@ DESCRIPTION
 -----------
 Reads the supplied diff output (i.e. "a patch") and applies it to files.
 With the `--index` option the patch is also applied to the index, and
-with the `--cache` option the patch is only applied to the index.
+with the `--cached` option the patch is only applied to the index.
 Without these options, the command applies the patch only to files,
 and does not require them to be in a git repository.