serviceability-cli: prune User test literals to only asserted fields

[ayushsingh82]

Progress on #4084

Summary of Changes

• test_cli_user_delete, test_cli_user_request_ban, and test_cli_user_update each build a full 22-field User literal only to hand it back through the mocked get_user. None of the three tests assert on any field of that value — execute() only cares that get_user returns a user so the command can proceed to delete_user/update_user/request_ban_user.
• Replaced each with User::default() (the manual impl Default for User added in serviceability: change user feed_pk to vec of feed_pks #4080), with a comment noting why no field is load-bearing.

This is a first, narrow slice of #4084 — scoped to smartcontract/cli/src/user/*. The issue also names smartcontract/sdk/rs and crates/doublezero-daemon-cli, which have their own User literals (some with fields that likely are asserted on and need per-test judgment, per the issue's caveat about User::default()'s non-neutral values). Left those for follow-up PRs rather than one large mechanical sweep, per the issue's own guidance.

Diff Breakdown

Category	Files	Lines (+/-)	Net
Tests	3	+14 / -80	-66
Total	3	+14 / -80	-66

Pure test cleanup — no production code touched.

Testing Verification

• cargo test --lib user:: in smartcontract/cli: all 29 user-module tests pass, including the 3 changed.
• cargo clippy --lib -- -Dclippy::all -D warnings: clean.
• Manually verified each of the 3 tests never reads a field of the user value it constructs — only its presence (via get_user returning Ok) drives the command under test.

[ayushsingh82]

@nikw9944 PR is up: prunes the User test literals in smartcontract/cli/src/user/* down to only the fields each test asserts on, per #4084. Ready for CI.

[ayushsingh82]

The only red check here is changelog / check-changelog; all 30 others pass. This PR is a test-only cleanup (pruning User literals in smartcontract/cli/src/user/* tests down to the asserted fields), no behavior change, so it seems like a skip-changelog case in line with #4094 / #4089. @nikw9944 could you add the label? Happy to add a CHANGELOG line instead if you'd prefer.