Update pydocstyle requirement from <4.0 to <7.0

Updates the requirements on [pydocstyle](https://github.com/PyCQA/pydocstyle) to permit the latest version.
- [Release notes](https://github.com/PyCQA/pydocstyle/releases)
- [Changelog](https://github.com/PyCQA/pydocstyle/blob/master/docs/release_notes.rst)
- [Commits](PyCQA/pydocstyle@0.1.0...6.3.0)

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

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

server/requirements.txt

@@ -3,7 +3,7 @@ nose-timer
 pep8
 flake8
 flake8-docstrings
-pydocstyle<4.0
+pydocstyle<7.0
 wooper==0.4.4
 requests
 requests-mock==1.12.1