check-ignore doc: fix broken link to ls-files page

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-check-ignore.txt

@@ -82,7 +82,7 @@ SEE ALSO
 --------
 linkgit:gitignore[5]
 linkgit:gitconfig[5]
-linkgit:git-ls-files[5]
+linkgit:git-ls-files[1]
 
 GIT
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