test_fail.sh: call /bin/sh

This is a simple shell script using no bash functionalty.

Closes: https://github.com/HowardHinnant/date/issues/854

test_fail.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/sh
 
 echo $1
 eval $1
@@ -7,4 +7,3 @@ if [ $? -eq 0 ]; then
 	exit 0;
 fi
 exit 1;
-