Update requirements

- removing unused footer

pages/custom_theme/footer.html

-{% block footer %}
-<p>{% if config.copyright %}
-<small>{{ config.copyright }}<br></small>
-{% endif %}
-<hr>
-Built with <a href="https://www.mkdocs.org/">MkDocs</a> using a <a href="https://github.com/snide/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
-{% if page and page.meta and page.meta.git_revision_date_localized %}
-<small><br><i>Last updated {{ page.meta.git_revision_date_localized }}</i></small>
-{% endif %}
-</p>
-{% endblock %}

pages/requirements.txt

-mkdocs==1.2.2
-mkdocs-git-revision-date-localized-plugin==0.10.3
-mkdocs-macros-plugin==0.6.3
-Jinja2==2.11.2
-MarkupSafe==1.1.1
+mkdocs==1.4.2
+mkdocs-git-revision-date-localized-plugin==1.1.0
+mkdocs-macros-plugin==0.7.0
+mkdocs-material==8.5.10
+mkdocs-material-extensions==1.1
+Jinja2==3.1.2
+MarkupSafe==2.1.1