[flake8-pie] Add fix safety section to PIE794

[MeGaGiGaGon]

Summary

Part of #15584

This PR adds a fix safety section to PIE794

I could not track down when this rule was initially implemented/made unsafe due how old it could be + multiple large refactors to ruff.

There is no comment/reasoning in the code given for the unsafety.

Here is a code example demonstrating why it should be unsafe, since removing any of the assignments would change program behavior playground

class A:
    x = 1
    x = 2
    print(x)

class B:
    x = print(3)
    x = print(4)

class C:
    x = [1,2,3]
    y = x
    x = y[1]

Test Plan

N/A, no tests affected.

[dylwil3]

Thanks! I think there's a more basic reason for unsafety here.

[github-actions]

ruff-ecosystem results

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Linter (preview)

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