docs: source-versioning tweaks from review (#34184)

Author: kay-kim

doc/user/content/ingest-data/postgres/source-versioning.md

@@ -187,7 +187,10 @@ In your upstream PostgreSQL database, drop the column `B` from the table `T`:
 ALTER TABLE T DROP COLUMN B;
 ```
 
-Dropping the column B will have no effect on `v3.T`.
+Dropping the column B will have no effect on `v3.T`. However, the drop affects
+`v2.T` and `v2.matview` from our earlier examples. When the user attempts to
+read from either, Materialize will report an error that the source table schema
+has been altered.
 
 ## Optional: Swap schemas
 

doc/user/shared-content/postgres-known-limitations.md

@@ -10,8 +10,7 @@ This section refer to the legacy [`CREATE SOURCE ... FOR
 ...`](/sql/create-source/postgres/) that creates subsources as part of the
 `CREATE SOURCE` operation.  To be able to handle the upstream column additions
 and drops, see [`CREATE SOURCE (New Syntax)`](/sql/create-source/postgres-v2/)
-and see [`CREATE SOURCE (New Syntax)`](/sql/create-source/postgres-v2/) and
-[`CREATE TABLE FROM SOURCE`](/sql/create-table).
+and [`CREATE TABLE FROM SOURCE`](/sql/create-table).
 
 {{< /note >}}