templates: spell ASCII in uppercase in pre-commit hook

The name of the encoding is ASCII, not ascii.
Signed-off-by: NRichard Hartmann <richih.mailinglist@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

templates/hooks--pre-commit.sample

@@ -15,13 +15,13 @@ else
 	against=4b825dc642cb6eb9a060e54bf8d69288fbee4904
 fi
 
-# If you want to allow non-ascii filenames set this variable to true.
+# If you want to allow non-ASCII filenames set this variable to true.
 allownonascii=$(git config hooks.allownonascii)
 
 # Redirect output to stderr.
 exec 1>&2
 
-# Cross platform projects tend to avoid non-ascii filenames; prevent
+# Cross platform projects tend to avoid non-ASCII filenames; prevent
 # them from being added to the repository. We exploit the fact that the
 # printable range starts at the space character and ends with tilde.
 if [ "$allownonascii" != "true" ] &&
@@ -32,7 +32,7 @@ if [ "$allownonascii" != "true" ] &&
 	  LC_ALL=C tr -d '[ -~]\0' | wc -c) != 0
 then
 	cat <<\EOF
-Error: Attempt to add a non-ascii file name.
+Error: Attempt to add a non-ASCII file name.
 
 This can cause problems if you want to work with people on other platforms.