DOC: Fix version switcher for stable docs

[QuLogic]

PR summary

This should stop the banner from showing up on stable.

PR checklist

• [n/a] "closes #0000" is in the body of the PR description to link the related issue
• [n/a] new and changed code is tested
• [n/a] Plotting related features are demonstrated in an example
• [n/a] New Features and API Changes are noted with a directive and release note
• Documentation complies with general and docstring guidelines

[story645]

Is this what's supposed to be fixed? And can it only be fixed after merging? This is taken from the artifacts job on this PR:

[QuLogic]

Yea, it won't be fixed until merged, as everything pulls that json file from devdocs.

[story645]

Not merging cause I'm confused how merging to main fixes issues w/ 3.9 docs - is this supposed to be backported-but I figure @QuLogic knows the answer to this.

[QuLogic]

All docs pull switcher.json from devdocs; there's no need to backport. The version just needs to match.