Fix version matching in docs version switcher dropdown

[niksirbi]

Description

What is this PR

• Bug fix
• Addition of a new feature
• Other

Why is this PR needed?

Quoting myself from this comment

there is one remaining snug: if you look at the version switcher dropdown at neuroblueprint.neuroinformatics.dev/latest/index.html, it displays "Choose version" no matter which version we've selected. The expected behaviour is for the currently selected version to be displayed there, as is the case for the NumPy docs website: numpy.org/doc/1.26/index.html

What does this PR do?

We think we've pinned down the issue to erroneous version matching in the conf.py file, see the discussion under neuroinformatics-unit/movement#668

This PR implements a fix suggested by @animeshsasan in this comment.

References

neuroinformatics-unit/movement#668

How has this PR been tested?

Not tested, the real test will happen upon merging to main.

Is this a breaking change?

No.

Does this PR require an update to the documentation?

No.

Checklist:

• The code has been tested locally
• Tests have been added to cover all new functionality
• The documentation has been updated to reflect any changes
• The code has been formatted with pre-commit