Fix regression print

GitHubActions/execute_test.sh

@@ -38,6 +38,6 @@ else
 	echo "Error : not All the tests passed"
 	echo "last line : '$last_line'"
 	echo "thierd_line_from_the_last : '$third_line_from_the_last'"
- 	[ -s 'regression.out' ] && [ ! -s 'regression.out' ] && cat 'regression.out'
+ 	[ -f 'regression.diff' ] && [ ! -s 'regression.diff' ] && cat 'regression.diff'
 	exit 1
 fi