feat: Remove alpha flag from customers API endpoints

The customers API is no longer in early access preview.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: louis-pre

codegen/data/paths.yaml

@@ -110,7 +110,6 @@
 
 /customers:
   title: Customers
-  alpha: "**Early Access Preview.** The customers API is currently in Alpha. We're actively developing it and seeking early feedback at [support@seam.co](mailto:support@seam.co). Expect breaking changes as we refine the design."
 
 /devices/unmanaged:
   title: Unmanaged Devices