[bugfix] No module named 'diffusers.models.unet_2d_condition'

[SolveProb]

Motivation

bugfix for No module named 'diffusers.models.unet_2d_condition'

Modification

The latest version of diffusers has modified its file organization structure.
Change import path for diffusers.

Checklist

Submitting this pull request means that,

Before PR:

• I have read and followed the workflow indicated in the CONTRIBUTING.md to create this PR.
• Pre-commit or linting tools indicated in CONTRIBUTING.md are used to fix the potential lint issues.
• [] Bug fixes are covered by unit tests, the case that causes the bug should be added in the unit tests.
• [] New functionalities are covered by complete unit tests. If not, please add more unit test to ensure the correctness.
• [] The documentation has been modified accordingly, including docstring or example tutorials.

After PR:

• [] If the modification has potential influence on downstream or other related projects, this PR should be tested with some of those projects.
• CLA has been signed and all committers have signed the CLA in this PR.

[CLAassistant]

All committers have signed the CLA.