Fix Progress Bar Updates in SD 1.5 PAG Img2Img pipeline

[painebenjamin]

What does this PR do?

StableDiffusionPAGImg2ImgPipeline does not properly update the progress bar during the denoising process, making progress silent when working in a terminal environment.

This PR brings this pipeline's progress bar functionality in line with other pipelines.

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• Did you read the contributor guideline?
• Did you read our philosophy doc (important for complex PRs)?
• Was this discussed/approved via a GitHub issue or the forum? Please add a link to it if that's the case. Too minor for an issue, I think.
• Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings. This brings the functionality in line with documentation, the other way around is not needed in this case.
• Did you write any new necessary tests? Correct me if I'm wrong but I believe the progress bar functionality is not exercised in any existing tests.

Who can review?

Anyone can review, but based on the subject matter, @yiyixuxu and @asomoza seem to be the right folks.

[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[asomoza]

thanks a lot for the fix, the progress_bar.update was missing in the original PR

[asomoza]

the failing test is unrelated (cogvideo)