Add migration guide pointers for removed policies, tokenizers, and featurizers.

.typo-ci.yml

@@ -86,6 +86,7 @@ excluded_words:
   - extractor
   - fbmessenger
   - featurization
+  - featurize
   - featurized
   - featurizer
   - featurizers

docs/docs/migration-guide.mdx

@@ -1237,6 +1237,25 @@ confidences. This change can affect the maximum confidence predicted by the
 However, the previous behavior can still be enforced by setting
 `ranking_length=10` and `renormalize_confidences=True`.
 
+#### Removed Policies
+
+Several dialogue policies that were deprecated in Rasa 2.x have been removed in Rasa 3.0.
+If you are migrating a config file with a removed policy,
+consult the following migration guides for the individual policies:
+
+- `FallbackPolicy` [migration guide](#manually-migrating-from-the-fallback-policy)
+- `TwoStageFallbackPolicy` [migration guide](#manually-migrating-from-the-two-stage-fallback-policy)
+- `MappingPolicy` [migration guide](#manually-migrating-from-the-mapping-policy)
+- `FormPolicy` [migration guide](#forms)
+- `SklearnPolicy` should be replaced with [TEDPolicy](/policies#ted-policy).
+  It is recommended to use the [default TEDPolicy config](/model-configuration#suggested-config) as a starting point.
+
+#### Removed Tokenizers and Featurizers
+
+The `ConveRTTokenizer`, `LanguageModelTokenizer`, and `HFTransformersNLP` featurizer
+components were deprecated in Rasa 2.x and have been removed in Rasa 3.0. See the
+[migration guide for Rasa 2.x](#deprecations-2) for replacing these components in your pipeline.  
+
 ## Rasa 2.7 to 2.8
 
 :::caution