docs: drop exact version pins on python dependencies

These old package versions cause issues in modern Python environments.

docs/requirements.txt

@@ -1,26 +1,26 @@
-certifi==2022.9.24
-charset-normalizer==2.1.1
-click==8.1.3
-ghp-import==2.1.0
-idna==3.4
-importlib-metadata==4.12.0
-Jinja2==3.1.2
-Markdown==3.3.7
-markdown-include==0.7.0
-MarkupSafe==2.1.1
-mergedeep==1.3.4
-mkdocs==1.4.2
-mkdocs-material==8.5.9
-mkdocs-material-extensions==1.1
-packaging==21.3
-Pygments==2.13.0
-pymdown-extensions==9.8
-pyparsing==3.0.9
-python-dateutil==2.8.2
-PyYAML==6.0
-pyyaml_env_tag==0.1
-requests==2.28.1
-six==1.16.0
-urllib3==1.26.12
-watchdog==2.1.9
-zipp==3.8.0
+certifi
+charset-normalizer
+click
+ghp-import
+idna
+importlib-metadata
+Jinja2
+Markdown
+markdown-include
+MarkupSafe
+mergedeep
+mkdocs
+mkdocs-material
+mkdocs-material-extensions
+packaging
+Pygments
+pymdown-extensions
+pyparsing
+python-dateutil
+PyYAML
+pyyaml_env_tag
+requests
+six
+urllib3
+watchdog
+zipp