Fix that/which grammar (System.Net)

[gewarren]

https://learn.microsoft.com/style-guide/a-z-word-list-term-collections/t/that-vs-which

(Hide whitespace changes.)

[learn-build-service-prod]

Learn Build status updates of commit 1d293cf:

✅ Validation status: passed

File	Status	Preview URL	Details
xml/System.Net.Http.Headers/ContentDispositionHeaderValue.xml	✅Succeeded	View
xml/System.Net.Http.Headers/ProductInfoHeaderValue.xml	✅Succeeded	View
xml/System.Net.Http.Headers/RangeConditionHeaderValue.xml	✅Succeeded	View
xml/System.Net.Http.Headers/RetryConditionHeaderValue.xml	✅Succeeded	View
xml/System.Net.Http/HttpResponseMessage.xml	✅Succeeded	View
xml/System.Net.PeerToPeer.Collaboration/PeerCollaboration.xml	✅Succeeded	View
xml/System.Net.PeerToPeer.Collaboration/PeerContact.xml	✅Succeeded	View
xml/System.Net.PeerToPeer/Cloud.xml	✅Succeeded	View
xml/System.Net.PeerToPeer/PeerName.xml	✅Succeeded	View
xml/System.Net.PeerToPeer/PeerNameResolver.xml	✅Succeeded	View
xml/System.Net.Security/SslStream.xml	✅Succeeded	View
xml/System.Net.Sockets/Socket.xml	✅Succeeded	View
xml/System.Net/HttpListener.xml	✅Succeeded	View
xml/System.Net/HttpListenerRequest.xml	✅Succeeded	View

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