fix: Cohere inconsistent embeddings and documents lengths

[sjrl]

I am looking into this issue #283 and found a bug that I think is unrelated.

Update:
Running the code in issue #283 shows that the changes in this branch do seem to help. See comment here.

Basically we were copying the embeddings so we'd end up with twice as many embeddings as documents. I don't think this will fix the error brought up in issue #283, but we should avoid doing this.

Additional:

• also fixed some failing integration tests

[sjrl]

Hey @ZanSara I'm noticing that the integration tests that require a Cohere API key are not running in CI. Is this on purpose or should we be able to run them?

[ZanSara]

Hey @sjrl, thank you for this PR! Let's split the two things though:

1. the bugfix in one PR, so I can approve it right away, and
2. issue + PR for the Cohere tests, we need to address that separately and other tests might need fixing

Thank you for your help!

[ZanSara]

Testing out the example code the improvement is evident! Thank you for fixing this one! 🤗

[illorca-verbi]

Thanks for this fix. When will the release be cut for https://pypi.org/project/cohere-haystack/?

[anakin87]

released: https://pypi.org/project/cohere-haystack/0.3.1/