upgrading page does not mention deprecation of `pgjwt`

# Improve documentation ## Link https://supabase.com/docs/guides/platform/upgrading#extensions Add a link to the page which needs improvement (if relevant) ## Describe the problem Is the documentation missing? Or is it confusing? Why is it confusing? The "infrastructure" page in the dashboard refers to the above link telling me I need to remove the `pgjwt` extension. There is no mention of that extension being deprecated in the documentation. The extensions page does mention it, so that's helpful. ## Describe the improvement A clear and concise description of the improvement. Add the `pgjwt` extension to the deprecated list. Also it would be nice if the page would tell you how to test if your application is using the extension. For pgjwt, just look for the `sign()` and `verify()` functions. ## Additional context Add any other context or screenshots that help clarify your question.