Remove formatter incompatibility warning for ISC001

[MichaReiser]

Summary

Remove the formatter incompatility warning from ISC001 because the formatter now:

• Tries to join implicit concatenated strings that fit on a single line
• Preserves implicit concatenated strings as mulitline for the few cases where the automatic-joining isn't supported

This PR adds a warning for lint.flake8-implicit-str-concat.allow-multiline = false if ISC001 is disabled.
This is not a new incompatibility, it's just that we forgot to add it.

Test Plan

See CLI tests

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.