update runtime env to fix read the docs

[walshmm]

Please review the developer documentation
on the wiki of this project that contains help and requirements.

Proposed changes

urllib3/urllib3#2168 (comment)

It looks like a dependency finally reached EOL, comment in the thread suggests adding this config should resolve the readthedocs builds failing.

What type(s) of changes does this code introduce?

Delete the items that do not apply

Bugfix #4587

Does this introduce a breaking change?

• No

What systems has this change been tested on?

-- needs to be tested on readthedocs build server --

Checklist

Update the following with a yes where the items apply. If you're unsure about any of them, don't hesitate to ask. This is
simply a reminder of what we are going to look for before merging your code.

• Yes. This PR is up to date with current the current state of 'develop'
• N/A. Code added or changed in the PR has been clang-formatted
• N/A. This PR adds tests to cover any new code, or to catch a bug that is being fixed
• N/A. Documentation has been added (if appropriate)

[prckent]

Thanks! It worked. I'll force merge it since it is docs only.