Fix UPDATING section on SqlAlchemy 1.4 scheme changes (#21887)

UPDATING.md

@@ -87,7 +87,7 @@ It was previously possible to have any extension for zip files in the DAGs folde
 
 ### You have to use `postgresql://` instead of `postgres://` in `sql_alchemy_conn` for SQLAlchemy 1.4.0+
 
-When you use SQLAlchemy 1.4.0+, you need ot use `postgresql://` as the database in the `sql_alchemy_conn`.
+When you use SQLAlchemy 1.4.0+, you need to use `postgresql://` as the scheme in the `sql_alchemy_conn`.
 In the previous versions of SQLAlchemy it was possible to use `postgres://`, but using it in
 SQLAlchemy 1.4.0+ results in:
 
@@ -98,8 +98,8 @@ SQLAlchemy 1.4.0+ results in:
 E       sqlalchemy.exc.NoSuchModuleError: Can't load plugin: sqlalchemy.dialects:postgres
 ```
 
-If you cannot change the prefix of your URL immediately, Airflow continues to work with SQLAlchemy
-1.3 and you can downgrade SQLAlchemy, but we recommend to update the prefix.
+If you cannot change the scheme of your URL immediately, Airflow continues to work with SQLAlchemy
+1.3 and you can downgrade SQLAlchemy, but we recommend updating the scheme.
 Details in the [SQLAlchemy Changelog](https://docs.sqlalchemy.org/en/14/changelog/changelog_14.html#change-3687655465c25a39b968b4f5f6e9170b).
 
 ### Passing `execution_date` to `XCom.set()`, `XCom.clear()`, `XCom.get_one()`, and `XCom.get_many()` is deprecated