[`Tests`] Update deprecated `output_type="numpy"` in test files and fix several typos

[tolgacangoz]

This pull request updates the deprecated output_type="numpy" to output_type="np" in the test files, and fixes several typos. @stevhliu

[tolgacangoz]

Sorry for the unrelated commit history. I reversed them.

[HuggingFaceDocBuilderDev]

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[tolgacangoz]

Yeah, that is not necessarily about timesteps. I am updating the docstring then?

[stevhliu]

Yeah, let's just keep the changes that are related to numpy --> np

[tolgacangoz]

I couldn't understand. Should I change timesteps to w in the get_guidance_scale_embedding()'s docstring? Plus, in the code, of course.

[stevhliu]

Sorry I wasn't clear before! Let's keep w in the code and change the docstring from timesteps to w.

1. Keep w in the code and change the docstring from timesteps to w.
2. Update the parameter description for it. Currently, it says "generate embedding vectors at these timesteps" but that's not the clearest or most accurate. Instead, let's say something like: "Generate embedding vectors with a specified guidance scale to subsequently enrich timestep embeddings."

[tolgacangoz]

There are lots of other deprecation warnings in tests. Can/Should I open another PR(s) to update them?

[stevhliu]

Yeah you can open a separate PR for the deprecation warnings. It'd be better to keep the focus of this PR on just numpy to np and updating the docstring from timestep to w with a clearer parameter description.

[tolgacangoz]

Thanks for reviewing and merging!