Hide `None` & `Any` token wildcards for Author and Milestone tokens in Epics filtering

What does this MR do and why?

Hides None and Any wildcards for Author and Milestone tokens in Epics filtering. This change affects both Epics and Roadmap filtering since they both share same filtering frontend code.

Screenshots or screen recordings

NA

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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