Update vendored Unsafe code

Author: andrewlock

tracer/dependabot/Datadog.Dependabot.Vendors.csproj

@@ -43,17 +43,14 @@
     <!-- https://www.nuget.org/packages/System.Memory/4.6.3 -->
     <PackageReference Include="System.Memory" Version="4.6.3" />
 
-    <!-- https://www.nuget.org/packages/System.Private.CoreLib/1.0.0 -->
-    <PackageReference Include="System.Private.CoreLib" Version="1.0.0" />
-
     <!-- https://www.nuget.org/packages/System.Reflection.Metadata.Interop/7.0.20 -->
     <PackageReference Include="System.Reflection.Metadata.Interop" Version="7.0.20" />
 
     <!-- https://www.nuget.org/packages/System.Reflection.Metadata/7.0.20 -->
     <PackageReference Include="System.Reflection.Metadata" Version="7.0.20" />
 
-    <!-- https://www.nuget.org/packages/System.Runtime.CompilerServices.Unsafe/1.0.0 -->
-    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="1.0.0" />
+    <!-- https://www.nuget.org/packages/System.Runtime.CompilerServices.Unsafe/6.1.2 -->
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Version="6.1.2" />
 
     <!-- https://www.nuget.org/packages/ICSharpCode.SharpZipLib/1.3.3 -->
     <PackageReference Include="ICSharpCode.SharpZipLib" Version="1.3.3" />