OrdereredDictionary<K,V> and the KeyNotFoundException

### Type of issue

Missing information

### Description

It would be nice if the subtle difference between the indexers for the non-generic and generic OrderedDictionary classes was called out as something to be aware of.

In the non-generic version, the indexer returns null if the key isn't found.

In the generic version, the KeyNotFoundException is thrown if the key isn't found.

This subtlety bit us today as we recently updated the non-generic version to the generic version.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.collections.generic.ordereddictionary-2.item?view=net-10.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Collections.Generic/OrderedDictionary`2.xml

### Document Version Independent Id

fda90b9c-d6f5-e8a1-f381-46dd197f9890

### Platform Id

59bdc0d2-f5e3-f0b9-0c27-d510734779b1

### Article author

@dotnet-bot