Add None back to remove_termination_string for a_resume in group chat

[heyitsaamir]

Why are these changes needed?

This looks like it was accidentally removed in #2804. Adding it back because it lead to some broken builds for us.

Related issue number

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[marklysze]

Thanks @heyitsaamir, yep it does look like the None wasn't kept in the a_resume only in resume. Looks good to me.