Update assembly references

Author: andrewlock

tracer/test/Datadog.Trace.Tests/Snapshots/PublicApiTests.Datadog.Trace.AssemblyReferencesHaveNotChanged.net6.0.verified.txt

@@ -38,6 +38,7 @@ System.ObjectModel, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d
 System.Reflection.Emit, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Emit.ILGeneration, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Emit.Lightweight, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
+System.Reflection.Metadata, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Primitives, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Runtime, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Runtime.CompilerServices.Unsafe, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a

tracer/test/Datadog.Trace.Tests/Snapshots/PublicApiTests.Datadog.Trace.AssemblyReferencesHaveNotChanged.netcoreapp3.1.verified.txt

@@ -42,6 +42,7 @@ System.ObjectModel, Version=4.1.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d
 System.Reflection.Emit, Version=4.1.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Emit.ILGeneration, Version=4.1.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Emit.Lightweight, Version=4.1.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
+System.Reflection.Metadata, Version=1.4.5.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Reflection.Primitives, Version=4.1.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Resources.ResourceManager, Version=4.1.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a
 System.Runtime, Version=4.2.2.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a