Remove stale ignored_columns entries from Member

[mroderick]

Problem

Closes #3016.

Member still listed two columns in ignored_columns, and both are long gone:

• can_log_in — dropped in a2e7de00 (2026-08-05)
• unsubscribed — dropped in 69347342 (2026-10-12, Remove unused unsubscribed column from members #3007)

ignored_columns belongs to live columns only, so the self.ignored_columns += %w[can_log_in unsubscribed] line goes entirely.

Changes

• Remove the line (the only ignored_columns entry on the model, so nothing remains of the list).

Acceptance

• Member.ignored_columns is [].
• Member.all.to_sql names no stale columns.
• Full suite passes: make test (1728 examples, 0 failures).
• rubocop app/models/member.rb clean.

Review notes

• Single-line, single-file diff. No schema change, no deploy risk: stale ignored_columns entries are tolerated by Rails, so this only removes dead configuration.