Bump System.Security.AccessControl from 4.5.0 to 4.6.0

Bumps [System.Security.AccessControl](https://github.com/dotnet/corefx) from 4.5.0 to 4.6.0.
- [Release notes](https://github.com/dotnet/corefx/releases)
- [Commits](https://github.com/dotnet/corefx/commits)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

System.IO.Abstractions.TestingHelpers/System.IO.Abstractions.TestingHelpers.csproj

@@ -40,7 +40,7 @@
     <ItemGroup Condition="'$(TargetFramework)' == 'netstandard1.4'">
         <PackageReference Include="System.Diagnostics.Contracts" Version="4.3.0" />
         <PackageReference Include="System.Runtime.Serialization.Formatters" Version="4.3.0" />
-        <PackageReference Include="System.Security.AccessControl" Version="4.5.0" />
+        <PackageReference Include="System.Security.AccessControl" Version="4.6.0" />
     </ItemGroup>
 
     <ItemGroup>