Python dependency: Bump testtools from 2.8.5 to 2.8.7 in /web/regression

[dependabot]

Bumps testtools from 2.8.5 to 2.8.7.

Changelog

Sourced from testtools's changelog.

2.8.7

Improvements
------------
* Fix an issue with ``iterate_tests``, which was recently changes to insist
  on accepting an instance of ``unittest.TestSuite``, breaking some users.
  (Jelmer Vernooij, [#584](https://github.com/testing-cabal/testtools/issues/584))


Improve the type annotations for testtools.testcase.TestCase.skipTest
(Stephen Finucane, #585)


Correct a URL in the README
(Steve Kowalik, #582)


2.8.6

Improvements

• Improve the type annotations for testtools.testcase.TestCase.assertRaises. This method will now be typed correctly when called as a method or as a context manager. (Stephen Finucane, #577, #578)

Commits

• a2c63cc Merge pull request #586 from stephenfin/release-2.8.7
• b2d6e71 release 2.8.7
• 2ce38cd Merge pull request #585 from stephenfin/typing
• 2e5845a typing: Correct type of TestCase.skipTest
• 8260ef7 Merge pull request #584 from testing-cabal/fix-iter-testscase
• badf516 Fix iterate_tests to handle non-TestSuite iterables like lists
• 9165a00 Merge pull request #582 from s-t-e-v-e-n-k/silly-typo-readme
• b3a095b Correct silly URL typo in README
• 51ceb05 Merge pull request #581 from testing-cabal/dependabot/pip/ruff-0.15.5
• f2a0f90 Bump ruff from 0.15.4 to 0.15.5
• Additional commits viewable in compare view

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[dependabot]

Looks like testtools is up-to-date now, so this is no longer needed.