requirements: update psyneulink-sphinx-theme requirement

Updates the requirements on [psyneulink-sphinx-theme](https://github.com/kmantel/psyneulink-sphinx-theme) to permit the latest version.
- [Release notes](https://github.com/kmantel/psyneulink-sphinx-theme/releases)
- [Commits](kmantel/psyneulink-sphinx-theme@1.2.2.0...v1.2.3.0)

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

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

doc_requirements.txt

@@ -1,3 +1,3 @@
-psyneulink-sphinx-theme<1.2.2.2
+psyneulink-sphinx-theme<1.2.3.1
 sphinx<4.2.1
 sphinx_autodoc_typehints<1.13.0