Add uk1.datadoghq.com as a supported Datadog site

[TalUsvyatsky]

What does this PR do?

Add `uk1.datadoghq.com` to the list of supported Datadog sites.

Motivation

New Datadog datacenter support.

Testing Guidelines

Updated existing test assertion in `src/index.spec.ts` to reflect the new site in the error message.

Additional Notes

N/A

Types of changes

• Misc (docs, refactoring, dependency upgrade, etc.)

Check all that apply

• This PR's description is comprehensive
• This PR impacts documentation, and it has been updated (or a ticket has been logged)
• This PR's changes are covered by the automated tests

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.69%. Comparing base (ed3659b) to head (bb6ceeb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #712   +/-   ##
=======================================
  Coverage   77.69%   77.69%           
=======================================
  Files          12       12           
  Lines        1112     1112           
  Branches      350      350           
=======================================
  Hits          864      864           
  Misses        118      118           
  Partials      130      130           

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