Fix: Add workItemType check for weight widget for epics

What does this MR do and why?

After Add weight widget definition options (!157705 - merged) to add configuration was merged , epic work items also have weight widget.

But since the frontend MR to read the configuration cannot be merged in the same milestone , this MR is a "temporary fix" till !158021 (merged) is merged in early 17.3

Please check this slack conversation for more context 🙇

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Before	After

How to set up and validate locally

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

1. Check that weight widget is to be shown for all applicable work item types other than epic