chore(deps): update dependency system.io.abstractions.testinghelpers to v16

Author: renovate-bot

PostfixNumberRemover.Tests/PostfixNumberRemover.Tests.csproj

@@ -9,7 +9,7 @@
     <PackageReference Include="nunit" Version="3.13.2" />
     <PackageReference Include="NUnit3TestAdapter" Version="3.13.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.11.0" />
-    <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="6.0.15" />
+    <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="16.1.20" />
   </ItemGroup>
 
   <ItemGroup>