Update RepoTasks.csproj

Author: wtgodbe

eng/tools/RepoTasks/RepoTasks.csproj

@@ -15,7 +15,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="NuGet.Packaging" Version="5.6.0" />
+    <PackageReference Include="NuGet.Packaging" Version="5.9.0" />
     <PackageReference Include="Microsoft.Extensions.DependencyModel" Version="2.1.0" />
   </ItemGroup>