Move substitutions outside of printf expression

On the advice of shellcheck

verify-script.template

@@ -5,7 +5,7 @@ FILE="{filename}"
 EXPECTED_HASH="{filehash}"
 
 if [ "$(sha256sum "$FILE" | awk '{print $1}')" = "$EXPECTED_HASH" ]; then
-	printf "File $FILE validated with message:\n$MESSAGE"
+	printf "File %%s validated with message:\\n%%s" "$FILE" "$MESSAGE"
 	exit 0
 else
 	echo "File $FILE is not valid"