Attempt to fix failing documentation builds

There's a version resolution issue with sphinx and sphinx_rtd_theme;
sphinx_rtd_theme just added support for sphinx 7 last week.
For some reason, recent docs builds are installing sphinx<2 and
sphinx_rtd_theme<0.5, and then installing and running sphinx 7.2.3 and
running it with sphinx_rtd_theme 0.4.3.

Hopefully, requesting newer versions in the pyproject.toml file will
fix this.

Failing build that pairs sphinx 7 with sphinx_rtd_theme 0.4.3:
https://readthedocs.org/projects/aqtinstall/builds/21735283/

pyproject.toml

@@ -71,8 +71,8 @@ check = [
     "packaging",
 ]
 docs = [
-    "sphinx>=5.0",
-    "sphinx_rtd_theme",
+    "sphinx>=7.0",
+    "sphinx_rtd_theme>=1.3",
     "sphinx-py3doc-enhanced-theme",
 ]