Migration 20 cannot be unapplied

[cliffordgama]

Python version
N/A

Django version
6.0.2

Package version
0.32.0

Current behavior (bug description)

uv run ./manage.py migrate admin_interface zero

Crashes with:

... (truncated)
    raise IrreversibleError(
        "Operation %s in %s is not reversible" % (operation, self)
    )
django.db.migrations.exceptions.IrreversibleError: Operation <RunPython <function default_link_selected at 0x772c44e9e560>> in admin_interface.0020_module_selected_colors is not reversible

**Expected behavior**
The migration should have `RunPython(..., reverse_code=<something>)`

PR incoming.