fix for #7365, prevent pipelines from overriding provided prompt embeds

[bghira]

What does this PR do?

Fixes #7365

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Who can review?

@sayakpaul @yiyixuxu

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[yiyixuxu]

why are all the tests failing?

[yiyixuxu]

can we look into the remaining failing tests?

[bghira]

wow, i hadn't expected all of those, or really looked into them until now. i'm not sure why this simple check made those tests fail. i am wondering if there's something i need to check first before assigning the prompt embeds 🤔 like whether we have any? should i try and run the unit tests locally again?

[bghira]

@yiyixuxu i was trying again today and make test doesn't work here as i guess i don't have the right version of pytest installed, and now running pip install diffusers[dev] but i think there must be a way to run this in a Docker container?

edit: after pip install diffusers[dev] it now works to run make test