Fix Read the Docs build for ubuntu-24.04

.readthedocs.yaml

@@ -4,8 +4,10 @@ submodules:
   include: all
 
 build:
-  os: ubuntu-20.04
+  os: ubuntu-24.04
   apt_packages:
+    - cmake
+    - doxygen
     - fonts-liberation
   tools:
     python: "3.11"

docs/conf.py

@@ -1,13 +1,13 @@
 #!/usr/bin/env python
 # -*- coding: utf-8 -*-
 import subprocess
+from importlib.metadata import PackageNotFoundError, version
 
 import sphinx_material
-from pkg_resources import DistributionNotFound, get_distribution
 
 try:
-    __version__ = get_distribution("celerite2").version
-except DistributionNotFound:
+    __version__ = version("celerite2")
+except PackageNotFoundError:
     __version__ = "dev"