Update docs.yml (#6493)

Bump python version, pin nr-utils

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Fix docs build CI bug.
- pydocmkardown depends on pydocspec 
-[ pydocspec was updated May
6](https://pypi.org/project/docspec-python/#history) (two days ago), and
includes a problematic dependency (`nr.utils` which is specified as
[nr-utils](https://github.com/NiklasRosenstein/python-docspec/blob/61d3e38c55d290da6197236357e1cdfe818d35b5/docspec-python/pyproject.toml#L14C5-L14C23).
This caused imports to fail.
- current fix is fixing the pydocspec version.
- Also using the opportunity to update the python version 3.8 -> 3.9 for
the docs build 0.2

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## Why are these changes needed?

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solves. -->

## Related issue number

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## Checks

- [ ] I've included any doc changes needed for
<https://microsoft.github.io/autogen/>. See
<https://github.com/microsoft/autogen/blob/main/CONTRIBUTING.md> to
build and test documentation locally.
- [ ] I've added tests (if relevant) corresponding to the changes
introduced in this PR.
- [ ] I've made sure all auto checks have passed.

Author: victordibia

.github/workflows/docs.yml

@@ -141,10 +141,11 @@ jobs:
       - name: setup python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.8"
+          python-version: "3.9"
       - name: pydoc-markdown install
         run: |
           python -m pip install --upgrade pip
+          pip install docspec==2.2.1 docspec-python==2.2.1
           pip install pydoc-markdown pyyaml termcolor
           # Pin databind packages as version 4.5.0 is not compatible with pydoc-markdown.
           pip install databind.core==4.4.2 databind.json==4.4.2