chore(duo): remove ask deprecation notice

Summary

Keep glab duo ask hidden (already was) but drop the deprecation message and scheduled removal date. The command remains functional — we're no longer planning to remove it, we just don't advertise it in docs or help.

Changes

• internal/commands/duo/ask/ask.go — drop the Deprecated: field on duoAskCmd; keep Hidden: true.
• internal/commands/duo/ask/ask_test.go — trim the TestAskCmd skip message to just the flakiness reason (the removal-date reference is gone).

Verification

• make gen-docs — no drift (docs already omitted ask because it was hidden).
• go test ./internal/commands/duo/ask/... — passes.
• ./bin/glab duo ask --help — command still functional, no deprecation banner.
• ./bin/glab duo --help — only cli listed under COMMANDS; ask stays hidden.

Test plan

• glab duo ask "how do I undo my last commit" still returns commands (no deprecation warning printed).
• glab duo --help does not list ask.
• glab duo ask --help still shows usage.