Retire fixed Rust module benchmark expectation

[DavidBakerEffendi]

Description

Retire the stale Bifrost expected-failure annotation after scheduled benchmark run #34443712253 showed exact module declaration navigation.

Key Changes:

• Remove the rust-parity-module-declaration-definition expected-failure overlay now that Bifrost returns the exact authored workflow token range.
• Update the overlay coverage invariant from ten expected failures to nine.

Touch Points:

• benchmarks/expectations/bifrost-expected-failures.yaml
• src/runners/bifrost.rs

Validation:

• Focused overlay invariant test passed.
• cargo run -- validate benchmarks/cases/rust-lsp-parity.yaml passed.
• git diff --check passed.
• Full cargo test: 259 passed, with three unrelated evaluation tests blocked by the existing gohugoio--hugo.tar.gz source hash mismatch; the initially stale overlay-count assertion was updated and then passed independently.
• Full corpus validation is blocked by the same Go source archive hash mismatch.
• cargo fmt --check reports only pre-existing drift in src/promotion.rs.