doc: do not depend on typed-ast

the typed-ast project was marked end of life since July 2023, and
not maintained anymore. since we build the document using readthedocs'
service, and in .readtherdocs.yml we use python 3.9, which comes with
ast module included by its standard library.

the typed-ast dependency was originally added in 30d4159, but now that
we are using python 3.9, there is no need to use this module anymore.

Signed-off-by: Kefu Chai <[email protected]>

Author: tchaikov

admin/doc-requirements.txt

@@ -13,7 +13,6 @@ sphinx-autodoc-typehints == 1.18.3
 sphinx-prompt
 sphinx_rtd_theme
 Sphinx-Substitution-Extensions
-typed-ast
 sphinxcontrib-mermaid
 sphinxcontrib-openapi
 sphinxcontrib-seqdiag