Deleting project.json didn't update references

This may only be an issue for built-in references.

Add and run this code in a manual trigger:
```
#r "Microsoft.Azure.Documents.Client"

using System;
using Microsoft.Azure.Documents;

public static void Run(string input, TraceWriter log)
{
log.Info(typeof(Document).Assembly.Location);
}
```
You'll see the location: `D:\Program Files (x86)\SiteExtensions\Functions\1.0.10690\bin\Microsoft.Azure.Documents.Client.dll`

Add this project.json and run again:
```
{
"frameworks": {
"net46": {
"dependencies": {
"Microsoft.Azure.DocumentDB": "1.13.1"
}
}
}
}
```
You can see logs that it was installed: `D:\home\data\Functions\packages\nuget\Microsoft.Azure.DocumentDB\1.11.1\lib\net45\Microsoft.Azure.Documents.Client.dll`

Delete the project.json (and project.lock.json) and run again: `D:\home\data\Functions\packages\nuget\Microsoft.Azure.DocumentDB\1.11.1\lib\net45\Microsoft.Azure.Documents.Client.dll`

It's still referencing the old assembly.

If you restart the site, it'll go back to the original.