docs: drop mike version provider for pre-1.0

mike maintains multiple versioned snapshots of the docs under one
domain, with a version dropdown for switching between them. Useful
once an API contract stabilizes and users on different installed
versions need to read the docs that match their install.

Pre-1.0, breaking changes are still expected — historical snapshots
would just confuse readers (the API in v0.5 docs may not exist in
v0.7). pydantic-ai's docs site (the polish reference) doesn't ship
versioned docs either. Revisit when 1.0 ships and the API
contract stabilizes.

Removes ``extra.version.provider: mike`` from mkdocs.yml so Material's
theme stops trying to fetch a versions.json that no CI step
produces.

Author: chris-colinsky

mkdocs.yml

@@ -113,11 +113,6 @@ nav:
 extra:
   # Hide the "Made with Material for MkDocs" footer.
   generator: false
-  # Versioned docs via mike. The dropdown shows once at least one
-  # version has been published (``mike deploy <version>``); pre-1.0
-  # it stays hidden because nothing's deployed.
-  version:
-    provider: mike
   social:
     - icon: fontawesome/brands/github
       link: https://github.com/LunarCommand/openarmature-python