Fix basic-chat flow.dag file for online-endpoint deployment

[ouphi]

Description

Proposition to fix the issue #666

The problem is that when following this tutorial to deploy an online-endpoint from the basic-chat example the online-endpoint does not work well, we get an error as described in the according issue.
Adding the provider and the module fixed the issue for me.

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[ouphi]

Closing this PR as the issue can be fixed in the example, by using a more recent promptflow image, as discussed in this issue #666