Fix dependabot pip errors

[leander-dsouza]

Description

• Fixes the series of failed deployment builds primarily due to the ubuntu: focal image at CircleCI.
• The dependencies have been bumped to ensure a clean build with the latest version of the libraries.
• get_html_theme_path() and display_version are removed as they are deprecated with the new version of Sphinx.

Testing

The following changes have been verified using make html and opening the _build/html/index.html file in a browser window.

[SteveMacenski]

I do not want to generically update sphinx and other libraries automatically. There are formatting and other changes that can occur on those adjustments and we need to be able to QA those change before they're accepted. Unless there's a specific reason to update certain versions or libraries, I air to the side of status quo on the docs to make the maintainer overhead as small as possible so we can focus attention on the main project.

[leander-dsouza]

Thank you for the feedback, Steve.
Yes, you are right that there are slight formatting changes with the updated libraries.

To reduce the maintainer overhead, I think I can revert the pip version checking of dependabot, as it checks the latest version of libraries, which only work with ubuntu:latest. Apologies for the oversight, as I can imagine the frustration of having a bunch of incompatible dependabot PRs appear at once.

Therefore, I can close this PR and make another to revert the Python changes in dependabot.

[SteveMacenski]

OK! Sounds good