Update sphinx requirement from <6 to <7 (#213)

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES)
- [Commits](sphinx-doc/sphinx@0.1.61611...v6.0.0)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:development
...

Signed-off-by: dependabot[bot] <[email protected]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

setup.cfg

@@ -42,7 +42,7 @@ dev =
     pytest-xdist<4
     responses==0.21.0
 docs =
-    sphinx<6
+    sphinx<7
     sphinx-issues<3
     furo==2022.6.21