db96e52d6f
Running a command like `tailscale up --auth-key tskey-foo --auth-key tskey-bar` used to print ``` invalid value "tskey-bar" for flag -auth-key: flag provided multiple times ``` but now we print ``` invalid value "tskey-REDACTED" for flag -auth-key: flag provided multiple times ``` Fixes #18562 Signed-off-by: Andrew Lytvynov <awly@tailscale.com>