Remove obsolete VS MEF dependency.

Author: allisterb

src/NugetAuditor.2019/NugetAuditor.VSIX.2019/source.extension.vsixmanifest

@@ -14,7 +14,6 @@
     </Installation>
     <Dependencies>
         <Dependency Id="Microsoft.Framework.NDP" DisplayName="Microsoft .NET Framework" d:Source="Manual" Version="[4.5,)" />
-        <Dependency Id="Microsoft.VisualStudio.MPF.16.0" DisplayName="Visual Studio MPF 16.0" d:Source="Installed" Version="[16.0,17.0)" />
     </Dependencies>
     <Assets>
         <Asset Type="Microsoft.VisualStudio.VsPackage" d:Source="Project" d:ProjectName="%CurrentProject%" Path="|%CurrentProject%;PkgdefProjectOutputGroup|" />