ao migration: remove package test as this behavior is tested by other things (#94422)
Summary:
We have tests testing package level migration correctness for torch AO migration.
After reading the code, I noticed that these tests are not testing anything
additional on top of the function level tests we already have.
An upcoming user warning PR will break this test, and it doesn't seem worth fixing.
As long as the function level tests pass, 100% of user functionality will
be tested. Removing this in a separate PR to keep PRs small.
Test plan:
```
python test/test_quantization.py -k AOMigration
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94422
Approved by: https://github.com/jcaip
