test(inbound): resolve CodeQL "assert has a side-effect" alerts

[tuyakhov]

What

CodeQL is flagging four "assert statement has a side-effect" alerts in
tests/test_inbound.py — the reason the CodeQL check is red on the base
inbound PR. Each is a delete() call placed directly inside an assert:

assert client.inbound.addresses.delete("inb_1") is True

Because assert is stripped under python -O, the delete would silently not
run. Fix: assign the result to a local, then assert on the value:

deleted = client.inbound.addresses.delete("inb_1")
assert deleted is True

Applied to all four flagged sites (sync + async, addresses + domains). No
behavior change — the requests still fire and the assertions still hold.

Verification

• ruff format --check / ruff check — clean
• pytest tests/test_inbound.py — 18 passed
• No remaining calls inside assert statements in the file

Targeted at the base inbound branch so its CodeQL check clears.

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Generated by Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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