DOC: Fix doc build for 2.5.x branch

[effigies]

Backports #390, and also attempts to pacify the following error from the build:

ERROR: setuptools==47.1.0 is used in combination with setuptools_scm>=8.x

Your build configuration is incomplete and previously worked by accident!
setuptools_scm requires setuptools>=61

Suggested workaround if applicable:
 - migrating from the deprecated setup_requires mechanism to pep517/518
   and using a pyproject.toml to declare build dependencies
   which are reliably pre-installed before running the build tools