docs: fix stale chaining notebook link in model cookbook

The Model Linking section linked to notebooks/imaging/advanced/chaining/
start_here.ipynb, which 404s after the workspace reorganisation; point it
at the current notebooks/guides/modeling/chaining.ipynb. All other
autolens_workspace links in the cookbook verified to resolve on main.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DHfvdagPTJDDEsTHcFnatQ

Author: claude

docs/general/model_cookbook.md

@@ -427,7 +427,7 @@ When performing non-linear search chaining, the inferred model of one phase can
 
 The following example notebooks show how to compose and fit these models:
 
-<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/imaging/advanced/chaining/start_here.ipynb>
+<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/guides/modeling/chaining.ipynb>
 
 ## Across Datasets (Advanced)