Pull Request Overview

This PR removes obsolete API difference suppressions from the SDK content tests, addressing issue #5378. The changes eliminate five suppression entries for various System attributes (ExperimentalAttribute, SetsRequiredMembersAttribute, CollectionBuilderAttribute, CompilerFeatureRequiredAttribute, and RequiredMemberAttribute) that were previously needed for the Microsoft.CodeAnalysis.Workspaces.MSBuild.BuildHost.dll in the dotnet-watch tool.

• Removed five CP0001 diagnostic suppressions for System attribute types
• All removed suppressions were related to the BuildHost-netcore component of dotnet-watch

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