Update the link to the api docs

The README.md under fass/api-docs has an incorrect URL to the api spec
file. This change updates it.

Fixes #1826

Signed-off-by: Varun S Lingaraju <[email protected]>

Author: warunsl

api-docs/README.md

@@ -1,11 +1,11 @@
 ## Exploring or editing the Swagger API documentation
 
-The `swagger.yml` file can be viewed and edited in the Swagger UI.
+The `spec.openapi.yml` file can be viewed and edited in the Swagger UI.
 
 * Head over to the [Swagger editor](http://editor.swagger.io/)
 
 * Now click File -> Import URL
 
-* Type in `https://raw.githubusercontent.com/openfaas/faas/master/api-docs/swagger.yml` and click OK
+* Type in `https://raw.githubusercontent.com/openfaas/faas/master/api-docs/spec.openapi.yml` and click OK
 
 You can now view and edit the Swagger, copy back to your fork before pushing changes.