Readthedocs builds are failing

[phargogh]

In several recent PRs (#463 #465 #467 #468 ), the readthedocs build has been failing in the PRs because of the following error that looks due to the deprecation (at long last) of pkg_utils.

Running Sphinx v8.2.3
--
  |  
  | Configuration error!
  |  
  | Versions
  | ========
  |  
  | * Platform:         linux; (Linux-6.8.0-1029-aws-x86_64-with-glibc2.35)
  | * Python version:   3.12.12 (CPython)
  | * Sphinx version:   8.2.3
  | * Docutils version: 0.21.2
  | * Jinja2 version:   3.1.6
  | * Pygments version: 2.19.2
  |  
  | Last Messages
  | =============
  |  
  | None.
  |  
  | Loaded Extensions
  | =================
  |  
  | None.
  |  
  | Traceback
  | =========
  |  
  | Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/config.py", line 601, in eval_config_file
  | exec(code, namespace)  # NoQA: S102
  | ^^^^^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/checkouts/latest/docs/source/conf.py", line 18, in <module>
  | from pkg_resources import get_distribution
  | ModuleNotFoundError: No module named 'pkg_resources'
  |  
  | The above exception was the direct cause of the following exception:
  |  
  | Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/cmd/build.py", line 414, in build_main
  | app = Sphinx(
  | ^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/application.py", line 266, in __init__
  | self.config = Config.read(self.confdir, confoverrides or {}, self.tags)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/config.py", line 357, in read
  | namespace = eval_config_file(filename, tags)
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/config.py", line 616, in eval_config_file
  | raise ConfigError(msg % traceback.format_exc()) from exc
  | sphinx.errors.ConfigError: There is a programmable error in your configuration file:
  |  
  | Traceback (most recent call last):
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/conda/latest/lib/python3.12/site-packages/sphinx/config.py", line 601, in eval_config_file
  | exec(code, namespace)  # NoQA: S102
  | ^^^^^^^^^^^^^^^^^^^^^
  | File "/home/docs/checkouts/readthedocs.org/user_builds/pygeoprocessing/checkouts/latest/docs/source/conf.py", line 18, in <module>
  | from pkg_resources import get_distribution
  | ModuleNotFoundError: No module named 'pkg_resources'
  |  
  |  
  | The full traceback has been saved in:
  | /tmp/sphinx-err-8mcybi1x.log
  |  
  | To report this error to the developers, please open an issue at <https://github.com/sphinx-doc/sphinx/issues/>. Thanks!
  | Please also report this if it was a user error, so that a better error message can be provided next time.