remove version plugin & update siteurl

[sarasafavi]

Related Issue(s):

Closes # #769

Proposed Changes:

For inclusion in changelog (if applicable):

1. N/A

Not intended for changelog:

1. updating docs config to fix 404 page (see also 404 page is not rendered properly when mkdocs-material is used readthedocs/readthedocs.org#9570)
2. removing mike to fix readthedocs' native version flyout

PR Checklist:

• This PR is as small and focused as possible
• If this PR includes proposed changes for inclusion in the changelog, the title of this PR summarizes those changes and is ready for inclusion in the Changelog.
• I have updated docstrings for function changes and docs in the 'docs' folder for user interface / behavior changes
• This PR does not break any examples or I have updated them

(Optional) @mentions for Notifications:

[sarasafavi]

@JuLeeAtPlanet for your awareness:

• this update to siteurl should fix the broken 404 page on readthedocs, see related known issue 404 page is not rendered properly when mkdocs-material is used readthedocs/readthedocs.org#9570

• I'm trying out removing mike to see if that resolves the broken version flyout on RTD, as mike is trying to set its on version picker and may be clobbering that of RTD