fix: avoid BuiltIn false positive for verb phrases

[jmolz]

Fixes #3288

Summary

• narrow the BuiltIn Weir rule so built in only lints in modifier+noun contexts
• add regression coverage for verb-phrase uses like "was built in 1962" and "was built in Rust"
• keep existing in-built and modifier suggestions covered

Tests

• cargo test -p harper-core run_tests_for_built_in
• cargo run -p harper-cli -- test harper-core/src/linting/weir_rules/BuiltIn.weir
• cargo fmt --all --check

[elijah-potter]

This looks good to me. Thanks!