[Accessibility]: Code Insights updating repo filter does not announce changes

[unclejustin]

Audit type

Screen reader navigation

User journey audit issue

https://github.com/sourcegraph/sourcegraph/issues/33499

Problem description

Changing either of the repo filters updates the graph preview. But the changes are not announced. A screen reader user would have no idea that these changes did anything.

Expected behavior

The screen reader announces that the preview has changed.

Additional details

No response

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Owner

This issue will be fixed by my team, I have assigned a relevant member to it, or I will do so in the near future.

/cc @Joelkw @felixfbecker @vovakulikov