docs: add version_metadata to non-inheritable keys

[sebws]

Summary

version_metadata is non-inheritable. although you could assume so as it seems related to vars, it isn't clear. this PR adds a line to mention it.

Screenshots (optional)

Documentation checklist

• Is there a changelog entry (guidelines)? If you don't add one for something awesome and new (however small) — how will our customers find out? Changelogs are automatically posted to RSS feeds, the Discord, and X.
• The documentation style guide has been adhered to.

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