Update model-contracts.md for supported models

Update to show that incremental models with on_schema_change: fail are actually supported.

Reformat to make what is and isn't supported clearer.

website/docs/docs/collaborate/govern/model-contracts.md

@@ -28,10 +28,18 @@ While this is ideal for quick and iterative development, for some models, consta
 ## Where are contracts supported?
 
 At present, model contracts are supported for:
-- SQL models. Contracts are not yet supported for Python models.
-- Models materialized as `table`, `view`, and `incremental` (with `on_schema_change: append_new_columns`). Views offer limited support for column names and data types, but not `constraints`. Contracts are not supported for `ephemeral`-materialized models.
+- SQL models. 
+- Models materialized as one of the following
+    - `table`
+    - `view`. Views offer limited support for column names and data types, but not `constraints`.
+    - `incremental` (with `on_schema_change: append_new_columns` or `on_schema_change: fail`).  
 - Certain data platforms, but the supported and enforced `constraints` vary by platform.
 
+Model contracts are **not** supported for:
+- Python models.
+- `ephemeral`-materialized SQL models.
+
+
 ## How to define a contract
 
 Let's say you have a model with a query like: