fix: Fix for cohere v4 embeddings

[3coins]

Fixes #682

[3coins]

Ran the integration tests locally to cover both v3 and v4.

tests/integration_tests/embeddings/test_bedrock_embeddings.py ......s............                                                                                       [100%]

============================================================================= slowest 5 durations =============================================================================
2.71s call     tests/integration_tests/embeddings/test_bedrock_embeddings.py::test_bedrock_cohere_embedding_large_document_set[cohere_embeddings1]
1.79s setup    tests/integration_tests/embeddings/test_bedrock_embeddings.py::test_bedrock_embedding_documents
1.65s call     tests/integration_tests/embeddings/test_bedrock_embeddings.py::test_bedrock_cohere_embedding_large_document_set[cohere_embeddings0]
0.75s call     tests/integration_tests/embeddings/test_bedrock_embeddings.py::test_bedrock_embedding_documents_multiple
0.61s call     tests/integration_tests/embeddings/test_bedrock_embeddings.py::test_bedrock_cohere_embedding_documents_multiple[cohere_embeddings1]
======================================================================= 18 passed, 1 skipped in 13.21s ========================================================================

[3coins]

@notfoundry
Do you want to try these changes, and let me know if there is any feedback before we merge?

[michaelnchin]

Thanks @3coins , LGTM 👍

[7AM7]

@3coins when you can release this ?