Bump ReportGenerator from 4.8.0 to 4.8.1 (OmniSharp#435)

Bumps [ReportGenerator](https://github.com/danielpalme/ReportGenerator) from 4.8.0 to 4.8.1.
- [Release notes](https://github.com/danielpalme/ReportGenerator/releases)
- [Commits](danielpalme/ReportGenerator@v4.8.0...v4.8.1)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Directory.Build.targets

@@ -17,7 +17,7 @@
     <ItemGroup>
         <PackageReference Update="GitVersion.Tool" Version="5.5.1" />
         <PackageReference Update="JetBrains.ReSharper.CommandLineTools" Version="2020.2.4" />
-        <PackageReference Update="ReportGenerator" Version="4.8.0" />
+        <PackageReference Update="ReportGenerator" Version="4.8.1" />
         <PackageReference Update="Rocket.Surgery.Nuke" Version="0.14.2" />
     </ItemGroup>
     <ItemGroup>