[Hacktoberfest] DeepFloyd IF docstrings

[stevhliu]

This feature request is included in this year's Diffusers Hacktoberfest 🎃!

Hacktoberfest's purpose is to give upcoming open-source developers the opportunity to learn about open-source and programming by fixing simple issues (like this one).

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Issue

For each of the DeepFloyd IF pipelines:

1. The encode_prompt parameters are all mixed up and need to be reformatted
2. The parameter values in __call__ are out of sync (for example, num_inference_steps should be 100 but the docstring says it is 50). Please also check if other values are also incorrect, like the guidance_scale

[m0saan]

@stevhliu I would like to work on this please!