Fix embedding model mismatch between Question_answering_using_embeddi…

[sheldonrampton]

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Summary

The article on "Embedding_Wikipedia_articles_for_search" is intended to show how the embeddings were generated for the article on "Question_answering_using_embeddings." However, the "Embedding_Wikipedia" code specifies a different EMBEDDING_MODEL than the "Question_answering" model. As a result, the "Question_answering" code fails to understand the embeddings and returns returns "I could not find an answer" when it tries to answer the questions. This pull request fixes that EMBEDDING_MODEL mismatch.