Fix Amazon Nova support

[dlqqq]

Problem

Users would like to use the new Amazon Nova models, announced at re:Invent 2024.

Proposed Solution

Allow Amazon Nova to be called through the Bedrock provider.

[dlqqq]

Amazon Nova can only be used through cross-region inference, so users have to manually type the inference profile ID (e.g. us.amazon.nova-pro-v1:0) into the Bedrock (custom/provisioned) provider.

However, when doing so, Jupyter AI currently replies with a blank message and an error log: