Fix broken 3.0 link (mongodb#266)

Author: mcmorisi

source/fundamentals/enterprise-authentication.txt

@@ -446,4 +446,4 @@ guide, see the following API Documentation:
 - `MongoClientSettings <{+new-api-root+}/MongoDB.Driver/MongoDB.Driver.MongoClientSettings.html>`__
 - `CreateGssapiCredential() <{+new-api-root+}/MongoDB.Driver/MongoDB.Driver.MongoCredential.CreateGssapiCredential.html>`__
 - `CreatePlainCredential() <{+new-api-root+}/MongoDB.Driver/MongoDB.Driver.MongoCredential.CreatePlainCredential.html>`__
-- `IOidcCallback <{+new-api-root+}/MongoDB.Driver/MongoDB.Driver.Core.Authentication.Oidc.IOidcCallback.html>`__
+- `IOidcCallback <{+new-api-root+}/MongoDB.Driver/MongoDB.Driver.Authentication.Oidc.IOidcCallback.html>`__