build(deps): bump testtools from 2.6.0 to 2.7.1

Bumps [testtools](https://github.com/testing-cabal/testtools) from 2.6.0 to 2.7.1.
- [Release notes](https://github.com/testing-cabal/testtools/releases)
- [Changelog](https://github.com/testing-cabal/testtools/blob/master/NEWS)
- [Commits](https://github.com/testing-cabal/testtools/compare/2.6.0...2.7.1)

---
updated-dependencies:
- dependency-name: testtools
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -94,7 +94,7 @@ sgmllib3k==1.0.0
 simple-websocket==1.0.0
 six==1.16.0
 soupsieve==2.5
-testtools==2.6.0
+testtools==2.7.1
 tlslite-ng==0.7.6
 tweepy==4.14.0
 # v4.6.0 breaks bases (which multiformats etc use)