build(deps): update testfixtures requirement from ~=8.2.0 to ~=8.3.0

Updates the requirements on [testfixtures](https://github.com/Simplistix/testfixtures) to permit the latest version.
- [Changelog](https://github.com/simplistix/testfixtures/blob/master/CHANGELOG.rst)
- [Commits](simplistix/testfixtures@8.2.0...8.3.0)

---
updated-dependencies:
- dependency-name: testfixtures
  dependency-type: direct:production
...

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

Author: dependabot[bot]

test-requirements.txt

@@ -1,3 +1,3 @@
 pytest~=7.2.2
 coverage~=7.2.2
-testfixtures~=8.2.0
+testfixtures~=8.3.0