Add note to Sentry OAuth configuration page (#14442)

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<!-- Use this checklist to make sure your PR is ready for merge. You may delete any sections you don't need. -->

## DESCRIBE YOUR PR
Added a note to the "OAuth Configuration (Recommended)" section on the Sentry MCP documentation page (`/product/sentry-mcp`). This note advises users to log out and back in to their LLM's MCP integration to refresh access if they've joined a new Sentry organization.

## IS YOUR CHANGE URGENT?  

Help us prioritize incoming PRs by letting us know when the change needs to go live.
- [ ] Urgent deadline (GA date, etc.): <!-- ENTER DATE HERE -->
- [ ] Other deadline: <!-- ENTER DATE HERE -->
- [x] None: Not urgent, can wait up to 1 week+

## SLA

- Teamwork makes the dream work, so please add a reviewer to your PRs.
- Please give the docs team up to 1 week to review your PR unless you've added an urgent due date to it.
Thanks in advance for your help!

## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs team](https://github.com/orgs/getsentry/teams/docs)

## LEGAL BOILERPLATE

<!-- Sentry employees and contractors can delete or ignore this section. -->

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

## EXTRA RESOURCES

- [Sentry Docs contributor guide](https://docs.sentry.io/contributing/)
```

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[Slack Thread](https://se

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Co-authored-by: Cursor Agent <[email protected]>

Author: jaffrepaul

docs/product/sentry-mcp/index.mdx

@@ -55,6 +55,10 @@ With OAuth configuration, you'll be prompted to:
 2. Login via your existing Sentry organization
 3. Grant access to the necessary permissions
 
+<Alert>
+  If you've joined a new Sentry organization, log out of your LLM's MCP integration and log back in to refresh access.
+</Alert>
+
 Once authenticated, you'll see the tools become available in your MCP client.
 
 ![Available Sentry MCP Tools](./img/mcp-tools.png)