Remove code snippets containing is_safetensors_available()

[chiral-carbon]

What does this PR do?

Fixes #4243

Some tests failing on running make test, since I did not add my own tests.
make test summary:

================================================== 116 failed, 1941 passed, 1145 skipped, 1098 warnings in 1420.89s (0:23:40) ===================================================

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Who can review?

@patrickvonplaten @DN6

[HuggingFaceDocBuilderDev]

The documentation is not available anymore as the PR was closed or merged.

[chiral-carbon]

The summary in the PR description above is the summary from make test that I run on my local machine.
I use a MacBook Pro 2019 and many of the above errors are MPS device errors, so I assume it is because I don't have GPU on my local machine that I see so many errors.

Need some help understanding the current AssertionErrors that you can see in the summary.

[DN6]

Hi @chiral-carbon PR looks good. I'd like to update/add some tests to this PR. Can add me as a collaborator to your fork so that I can commit them? Alternatively, I can create another with the test changes that you can merge into your branch. LMK what works for you 👍🏽

[chiral-carbon]

Thanks @DN6! I think I would like to merge your test commits from your own fork. If that is a longer process though I will directly add you as collaborator.

[DN6]

@chiral-carbon Could you merge the commits from safetensors-default into your branch.

[chiral-carbon]

@DN6 let me know if I merged the commits correctly. I'll look into why one test still fails

[DN6]

@chiral-carbon Pushed up a fix for that test. If you could merge it from the same branch I think we should be good

[chiral-carbon]

it works @DN6, thanks! I was stuck on the logic in the last tests so this helps me understand too

[DN6]

Hi @chiral-carbon requesting one last small change. I think we can get rid of these lines in the test. We don't need them anymore.

diffusers/tests/models/test_modeling_common.py

Lines 63 to 65 in ac1580a

	import diffusers
	diffusers.utils.import_utils._safetensors_available = True

[DN6]

Great job @chiral-carbon 🙌🏽

[chiral-carbon]

@DN6 thanks for all your help!