Fixes broken relative link in README.md

Author: k-rush

README.md

@@ -15,7 +15,7 @@ This sample contains a web API running on ASP.NET Core 2.0 protected by Azure AD
 ### More information
 For more information about how the protocols work in this scenario and other scenarios, see [Authentication Scenarios for Azure AD](http://go.microsoft.com/fwlink/?LinkId=394414).
 
-> This sample has been updated to ASP.NET Core 2.0. Looking for previous versions of this code sample? Check out the tags on the [ASP.NET Core 1.0](./tree/aspnet10) branch.
+> This sample has been updated to ASP.NET Core 2.0. Looking for previous versions of this code sample? Check out the tags on the [ASP.NET Core 1.0](../../tree/aspnet10) branch.
 
 > This sample is for Azure AD v1.0. If you are looking for an Azure AD v2.0 sample (to sign-in users with Work and School accounts **and Microsoft Personal accounts**, please look at [active-directory-aspnetcore-webapp-openidconnect-v2](https://github.com/Azure-Samples/active-directory-aspnetcore-webapp-openidconnect-v2)