MAINT: Upgrade to sphinx-jupyterbook-latex~=0.4.6 (#1538)

* MAINT: Upgrade to sphinx-jupyterbook-latex~=0.4.6

* restrict rtd to sphinx<=4.2

* pin to sphinx==4.2

* fix yml formatting

* reconfigure rtd to use docs/requirements.txt

* use install settings (as before) in readthedocs.yml

* update sphinx4 fixtures for pydata-sphinx-theme and sphinx>=4.3 (latest release)

* pydata-sphinx-theme is now updated

* fix indendation