fix: repair bcos formula test block

[pengshenghai]

Summary

• replace the unsupported write_file call in the BCOS formula test block with Pathname#write
• remove || true from test commands so brew test does not mask failures
• compare the CLI version output with version.to_s instead of hard-coding 1.8.0

Scope

This only changes Formula/bcos.rb test-block behavior. It does not alter the tarball URL, SHA, install block, package source, or formula metadata.

Validation

• ruby -c Formula/bcos.rb -> Syntax OK
• git diff --check -- Formula/bcos.rb -> passed (Windows line-ending warning only)

I could not run brew test in this Windows workspace because Homebrew is not installed here.

AI assistance

Implemented with OpenAI Codex assistance after reading issue #8 and the current formula.