convex-backend PR 111: Fix self-hosted guide (#37839)

## PR Summary
This small PR fixes the `self-hosted/README.md` reference in `CONTRIBUTING.md`.

Co-authored-by: Emmanuel Ferdman <[email protected]>
GitOrigin-RevId: a81e34c90dbfbf0ca98c8d9d1ae9f551f0cc6f9e

Author: 2 people

CONTRIBUTING.md

@@ -31,4 +31,4 @@ Instructions for building and running Convex packages locally:
 
 Note: If you just want to self-host Convex and not modify the codebase, we
 recommend using the pre-built Docker image or binary. See the
-[self-hosted README](../self-hosted/README.md) for more information.
+[self-hosted README](self-hosted/README.md) for more information.