docs: fix dead links in README

Noticed a couple of dead links in the README doc. One is a typo
(AUTHENTICATION.md should be Authentication.md) so I fixed that.

The other pointed at a doc on VCAP_SERVICES that doesn't exist
any more, so I changed it for the only description I could find
for VCAP_SERVICES on the public cloud docs site.

Signed-off-by: Dale Lane <[email protected]>

Author: dalelane

README.md

@@ -59,7 +59,7 @@ Watson services are migrating to token-based Identity and Access Management (IAM
 
 Authentication is accomplished using dedicated Authenticators for each authentication scheme. Import authenticators from `ibm-watson/auth` or rely on externally-configured credentials which will be read from a credentials file or environment variables.
 
-To learn more about the Authenticators and how to use them with your services, see [the detailed documentation](https://github.com/IBM/node-sdk-core/blob/master/AUTHENTICATION.md).
+To learn more about the Authenticators and how to use them with your services, see [the detailed documentation](https://github.com/IBM/node-sdk-core/blob/master/Authentication.md).
 
 ### Getting credentials
 
@@ -164,7 +164,7 @@ assistant.setServiceUrl('<url_as_per_region>')
 When uploading your application to IBM Cloud there is a certain priority Watson services will use when looking for proper credentials. The order is as follows:
 1. Programmatic (i.e. IamAuthenticator)
 2. Credentials File
-3. VCAP_SERVICES (an environment variable used by IBM Cloud, details found [here](https://cloud.ibm.com/docs/watson?topic=watson-vcapServices))
+3. VCAP_SERVICES (an environment variable used by IBM Cloud, details found [here](https://cloud.ibm.com/docs/cloud-foundry-public?topic=cloud-foundry-public-deployingapps#app_env))
 
 ## Setting the Service URL
 You can set or reset the base URL after constructing the client instance using the `setServiceUrl` method: