Remove direct Microsoft.NETCore.Platforms dependency.

- Microsoft.NETCore.App now pulls this package in.

aspnet/Coherence-Signed#344

Author: N. Taylor Mullen

src/Microsoft.VisualStudio.Web.BrowserLink.Loader/project.json

@@ -13,7 +13,6 @@
     "Microsoft.AspNetCore.Http.Abstractions": "1.0.0-*",
     "Microsoft.Extensions.FileProviders.Physical": "1.0.0-*",
     "Microsoft.Extensions.PlatformAbstractions": "1.0.0-*",
-    "Microsoft.NETCore.Platforms": "1.0.1-*"
   },
   "frameworks": {
     "net451": {},