Suggest you make a copy of script, make your changes and then point the policy to your modified version.

You will need to create a new policy and add this script module to it as a script execution. Once it's added, you'll have the option to configure the parameters for the script. One of the parameters is "Special Characters". Remove the characters from that list that you don't want to be used in the password generation.

Thanks Nick, I was able to do that. Now how would i add this newly created script to the existing policy (Built-in Policy - Password Generation for Undo Deprovisioning) , Will i need to create a new policy here too? Do you have a process on how to create a custom policy for Password Generation for Undo Deprovisioning & add a newly created Script Module.

You will have to create a new policy because the built-in policy can't be modified. You'll just choose a Deprovisioning Policy instead of a Provisioning policy and add it the exact same way. They'll basically be identical except for when they're executed. If you make a change to any parameters on one, always make sure to update the parameters on the other as well because those settings are stored on the policy objects.