docs: add troubleshooting for slow performance (#5794)

## Description

Add a troubleshooting section for slow performance in the LSP server
advising users on steps to mediate it.

## Checklist

- [ ] I have linked to any relevant issues.
- [x] I have commented my code, particularly in hard-to-understand
areas.
- [x] I have updated the documentation where relevant (API docs, the
reference, and the Sway book).
- [ ] If my change requires substantial documentation changes, I have
[requested support from the DevRel
team](https://github.com/FuelLabs/devrel-requests/issues/new/choose)
- [ ] I have added tests that prove my fix is effective or that my
feature works.
- [ ] I have added (or requested a maintainer to add) the necessary
`Breaking*` or `New Feature` labels where relevant.
- [x] I have done my best to ensure that my PR adheres to [the Fuel Labs
Code Review
Standards](https://github.com/FuelLabs/rfcs/blob/master/text/code-standards/external-contributors.md).
- [ ] I have requested a review from the relevant team or maintainers.

---------

Co-authored-by: Sophie Dankel <47993817+sdankel@users.noreply.github.com>

Author: hummusonrails

docs/book/src/lsp/troubleshooting.md

@@ -14,6 +14,18 @@ Second, confirm that your `$PATH` resolves to the `forc-lsp` binary in `$HOME/.f
 which forc-lsp
 ```
 
+## Slow Performance
+
+If you are experiencing slow performance, you can try the following:
+
+Follow [the steps above](#troubleshooting) to ensure you are running the most recent version.
+
+Then, make sure you only have the most recent version of the LSP server running.
+
+```sh
+pkill forc-lsp
+```
+
 ## Server Logs
 
 You can you enable verbose logging of the LSP server.