Lucene.Net.Util.Events.TestPubSubEvent::CanAddSubscriptionWhileEventIsFiringNonGeneric(): Added [Ignore] attribute

[NightOwl888]

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Lucene.Net.Util.Events.TestPubSubEvent::CanAddSubscriptionWhileEventIsFiringNonGeneric(): Added [Ignore] attribute.

See #998

Description

Lucene.Net.Util.Events.TestPubSubEvent::CanAddSubscriptionWhileEventIsFiringNonGeneric(): Added [Ignore] attribute, as this only applies prior to .NET Standard 2.1 and was an inherited problem from Prism.Core. This problem will eventually go away when every target below netstandard2.1 is dropped and it doesn't seem like a priority to fix it unless a user reports a problem related to using weak events as a workaround to the fact that ConditionalWeakTable<TKey, TValue> didn't have an enumerator in older target frameworks.