remove NuGet package checks

Author: lanlanlee2008

src/SQLOutputCacheAsyncProvider/Microsoft.AspNet.OutputCache.SQLAsyncOutputCacheProvider.csproj

@@ -92,10 +92,6 @@
     <PropertyGroup>
       <ErrorText>This project references NuGet package(s) that are missing on this computer. Use NuGet Package Restore to download them.  For more information, see http://go.microsoft.com/fwlink/?LinkID=322105. The missing file is {0}.</ErrorText>
     </PropertyGroup>
-    <Error Condition="!Exists('..\..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props'))" />
-    <Error Condition="!Exists('..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.0\build\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.1.0.0\build\Microsoft.CodeDom.Providers.DotNetCompilerPlatform.props'))" />
-    <Error Condition="!Exists('..\..\packages\Microsoft.Net.Compilers.2.1.0\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.Net.Compilers.2.1.0\build\Microsoft.Net.Compilers.props'))" />
-    <Error Condition="!Exists('..\..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props')" Text="$([System.String]::Format('$(ErrorText)', '..\..\packages\Microsoft.Net.Compilers.1.0.0\build\Microsoft.Net.Compilers.props'))" />
   </Target>
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.