Add Turing Data Safe Haven description to evaluation page

[edwardchalstrey1]

:white_check_mark: Checklist

• [x] This pull request has a meaningful title.
• [ ] If your changes are not yet ready to merge, you have marked this pull request as a draft pull request.

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:arrow_heading_up: Summary

I noticed that an explanation of what the Turing Data Safe Haven actually is was missing, I've added one and clarified the TRE is this + institutional governance.

:closed_umbrella: Related issues

:raising_hand: Acknowledging contributors

• [ ] All contributors to this pull request are already named in the table of contributors in the README file.
• [ ] The following people should be added to the table of contributors in the README file:

[manics]

You can also ignore the URL in the linkchecker by adding it to https://github.com/sa-tre/satre-specification/blob/3f782c148cf9a706f873a4a667eb1c344af83606/docs/source/conf.py#L37-L39 If you do please include a comment explaining why (some sort of anti-DOS protection?)

[edwardchalstrey1]

You can also ignore the URL in the linkchecker by adding it to

https://github.com/sa-tre/satre-specification/blob/3f782c148cf9a706f873a4a667eb1c344af83606/docs/source/conf.py#L37-L39

If you do please include a comment explaining why (some sort of anti-DOS protection?)

No idea tbh! I think I'll leave out anyway, probably isn't really needed to link to the Turing website and better to just have the one link to the actual DSH codebase so if anything that's what people click