Either remove or update link to Evaluation issue(s)

[Malvoz]

In https://github.com/Maps4HTML/MapML-Proposal#use-cases-and-requirements:

Use Cases and Requirements

This proposal is being evaluated [...]

The link destination for "evaluated" is out of date since these issues were transferred and should now exist or be raised here: https://github.com/Maps4HTML/UCR-MapML-Matrix/issues.

We should either remove this link or update it to point to the correct repo (in which case we need to create a new label in UCR-MapML-Matrix, e.g. requirements evaluation, and add it to that one existing issue).

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Any change should be reflect on the same link in https://maps4html.org/MapML/spec/#use-cases-and-requirements.