docs: point multi-dataset example links at the renamed multi_dataset package

The `multi` example package in autolens_workspace is renamed to
`multi_dataset` (autolens_workspace#408). This updates the doc links and
prose that point into it.

Docs-only — no library source touched.

`bound: multi` in the non_linear.yaml configs is a Dynesty search
kwarg and is deliberately left alone.

MERGE ORDER: this must merge *after* the autolens_workspace rename PR,
since these are `blob/main` URLs that 404 until the package moves.

Refs PyAutoLabs/autolens_workspace#408

Author: Jammy2211

docs/general/model_cookbook.md

@@ -436,7 +436,7 @@ but certain parameters are free to vary across the datasets.
 
 The following example notebooks show how to compose and fit these models:
 
-<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/multi/start_here.ipynb>
+<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/multi_dataset/start_here.ipynb>
 
 ## Relations (Advanced)
 
@@ -445,7 +445,7 @@ We can compose models where the free parameter(s) vary according to a user-speci
 
 The following example notebooks show how to compose and fit these models:
 
-<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/multi/features/wavelength_dependence/modeling.ipynb>
+<https://github.com/PyAutoLabs/autolens_workspace/blob/main/notebooks/multi_dataset/features/wavelength_dependence/modeling.ipynb>
 
 ## PyAutoFit API
 

docs/overview/overview_3_features.md

@@ -166,7 +166,7 @@ The appearance of the strong changes as a function of wavelength, therefore mult
 more about the different components in a galaxy (e.g a redder bulge and bluer disk) or when imaging and interferometer
 data are combined, we can compare the emission from stars and dust.
 
-Checkout the `autolens_workspace/*/multi` package to get started, however combining datasets is a more advanced
+Checkout the `autolens_workspace/*/multi_dataset` package to get started, however combining datasets is a more advanced
 feature and it is recommended you first get to grips with the core API.
 
 ### Ellipse Fitting