fix: nargo fmt for backported nested_utility tests

[AztecBot]

Summary

CI3 on PR #23080 failed in the noir-projects build prep step because the new nested_utility_contract/src/test.nr (added by the backport of #23064 — feat(txe) authorize cross-contract utility calls) wasn't formatted by v4-next's pinned nargo. Three statements were committed multi-line that v4-next's nargo fmt --check wants on a single line.

CI log: http://ci.aztec-labs.com/0ef270f34a64bc9b

Fix

Apply nargo fmt exactly per the CI diff:

• same_contract_utility_call_from_private_succeeds: collapse the let result: Field = env.call_private(...) to one line.
• cross_contract_utility_call_from_utility_denied_by_default: collapse the env.execute_utility( ..., ) to one line.
• cross_contract_utility_call_from_private_denied_by_default: collapse the env.call_private( account, ..., ) to one line.

The two *_with_authorization tests already use multi-line because their bodies are too wide for one line — left unchanged.

Test plan

• CI3 on PR chore: Accumulated backports to v4-next #23080 should clear the prep step (noir-projects build) once this lands on backport-to-v4-next-staging.

ClaudeBox log: https://claudebox.work/s/ea70ef48e7a85dfe?run=3