Update sphinx requirement from <6.0.0,>=4.2.0 to >=4.2.0,<7.0.0 (#852)

* Update sphinx requirement from <6.0.0,>=4.2.0 to >=4.2.0,<7.0.0

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@v4.2.0...v6.1.3)

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

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

* Update intersphinx_mapping to sphinx>1.0 format

---------

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

Author: dependabot[bot]

doc/source/conf.py

@@ -238,7 +238,10 @@
 # -- Options for intersphinx extension ---------------------------------------
 
 # Example configuration for intersphinx: refer to the Python standard library.
-intersphinx_mapping = {'https://docs.python.org/': None}
+intersphinx_mapping = {
+        'python': ('https://docs.python.org/', None),
+        }
+
 
 # -- Options for todo extension ----------------------------------------------
 

requirements/docs.txt

@@ -1,6 +1,6 @@
 # dependencies for building docs, separate from dev.txt as this is also used for builds on readthedocs.org
 # core dependencies
-sphinx>=4.2.0, <6.0.0
+sphinx>=4.2.0, <7.0.0
 sphinx-autodoc-typehints>=1.12.0, <1.21  # limited due to https://github.com/tox-dev/sphinx-autodoc-typehints/issues/260
 sphinx-rtd-theme>=1.0.0, <2.0.0
 myst-parser>=1.0, <2.0