Fix doc build performance (#17748)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

docs/source/conf.py

@@ -60,9 +60,6 @@ autodoc2_packages = [
 autodoc2_output_dir = "api"
 autodoc2_render_plugin = "myst"
 autodoc2_hidden_objects = ["dunder", "private", "inherited"]
-autodoc2_docstring_parser_regexes = [
-    (".*", "docs.source.autodoc2_docstring_parser"),
-]
 autodoc2_sort_names = True
 autodoc2_index_template = None
 

requirements/docs.txt

 sphinx==7.4.7
 sphinx-argparse==0.5.2
-sphinx-autodoc2==0.5.0
 sphinx-book-theme==1.1.4
 sphinx-copybutton==0.5.2
 sphinx-design==0.6.1
@@ -9,6 +8,10 @@ myst-parser==3.0.1  # `myst-parser==4.0.1` breaks inline code in titles
 msgspec
 commonmark # Required by sphinx-argparse when using :markdownhelp:
 
+# Custom autodoc2 is necessary for faster docstring processing
+# see: https://github.com/sphinx-extensions2/sphinx-autodoc2/issues/33#issuecomment-2856386035
+git+https://github.com/hmellor/sphinx-autodoc2.git # sphinx-autodoc2==0.5.0
+
 # packages to install to build the documentation
 cachetools
 -f https://download.pytorch.org/whl/cpu