Do not set the app_id in remote_api, use the default one
Do not set the app_id in remote_api, use the default one

Fixes tools/remote_api.py that started failing post HRD migration with:
BadRequestError: app s~chromiumcodereview-hr cannot access app
chromiumcodereview-hr's data

By not specifying the app_id manually, the remote endpoint selects
the valid app_id automatically and "it just works".

Review: https://codereview.appspot.com/6889051/

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