docs: Add note regarding Vercel braching synchronization (supabase#30969)

Author: kamilogorek

apps/docs/content/guides/deployment/branching.mdx

@@ -580,7 +580,7 @@ With the Supabase branching integration, you can sync the Git branch used by the
 
 ### Vercel
 
-<Admonition type="note" label="Vercel Branching support is in development.">
+<Admonition type="note" label="Vercel Marketplace support.">
 
     The Vercel Integration for Supabase branching is working only with Supabase managed projects. There is currently no support for Vercel Marketplace managed resources, however the support is planned in the future.
 
@@ -598,10 +598,12 @@ For branching to work with Vercel, you also need the [Vercel GitHub integration]
 </Admonition>
 
 Supabase automatically updates your Vercel project with the correct environment variables for the corresponding preview branches.
+The synchronization happens at the time of Pull Request being opened, not at the time of branch creation.
+As branching integration is tied to the Preview Deployments feature in Vercel, there are possible race conditions between Supabase setting correct variables, and Vercel running a deployment process. Because of that, Supabase is always automatically re-deploying the most recent deployment of the given pull request.
 
-### Netlify
+## Other Git providers
 
-A Netlify integration is under consideration. If you're interested in branching with Netlify, [join the GitHub discussion](https://github.com/orgs/supabase/discussions/18938).
+There are multiple alternative Git providers under consideration. If you're interested in branching for GitLab, Bitbucket, or some other provider, [join the GitHub discussion](https://github.com/orgs/supabase/discussions/18938).
 
 ## Alternatives to branching