Update resource.js

This change is wrong and will make the example non-working.

It is a "GET" action and the object passed is a `params`(not a `data`) object.
Path-parameters are looker for by name in the `params` object (so ngResource will look for `userId`).
The mapping to `id` is only for the `data` object (which is only available in "non-GET" actions).

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This has also been discussed in #8948. Take a look at https://github.com/angular/angular.js/issues/8948#issuecomment-55521687) for a more detailed explanation.