sample pre-commit hook: use --bool when retrieving config var

Currently if you set

	[hooks]
		allowNonAscii

(or allownonascii = 1, or = yes) in your .git/config then the sample
pre-commit misinterprets the value as "false" and rejects non-ASCII
filenames.  Use "git config --bool" to get the usual nicer boolean
handling.

Signed-off-by: Johan Herland <johan@herland.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

templates/hooks--pre-commit.sample

@@ -16,7 +16,7 @@ else
 fi
 
 # If you want to allow non-ASCII filenames set this variable to true.
-allownonascii=$(git config hooks.allownonascii)
+allownonascii=$(git config --bool hooks.allownonascii)
 
 # Redirect output to stderr.
 exec 1>&2