[`flake8-bugbear`] Mark `B905` and `B912` fixes as unsafe (#20695)
Resolves https://github.com/astral-sh/ruff/issues/20694
This PR updates the `zip_without_explicit_strict` and
`map_without_explicit_strict` rules so their fixes are always marked
unsafe, following Brent's guidance that adding `strict=False` can
silently preserve buggy behaviour when inputs differ. The fix safety
docs now spell out that reasoning, the applicability drops to `Unsafe`,
and the snapshots were refreshed so Ruff clearly warns users before
applying the edit.
