fix: docs build (#1257)

Sphinx 7.2.0 breaks Breathe, see sphinx-doc/sphinx#11605 for now pin to 7.1.2 until either of them resolve this issue

.github/workflows/build-docs.yaml

@@ -33,6 +33,7 @@ jobs:
         run: |
           sudo apt install -y doxygen
           python3 -m pip install \
+              sphinx==7.1.2 \
               sphinxcontrib.plantuml \
               recommonmark \
               cloud_sptheme \