Remove linter configs and update language/dependency versions

[ydesgagn]

Summary

This PR removes several local linter configuration files and bumps a handful of language runtimes and dependency versions. The linter config files (.markdownlint-cli2.yaml, .rubocop.yml, .shellcheckrc, .yamllint.yml) are no longer needed locally and have been deleted. Language runtime versions for Go, Node.js, and PHP have been refreshed, the Redis option default has been pinned to 9.0, and multi_xml has been bumped in Gemfile.lock. The .gitignore has also been updated to exclude generated docs/code-review.md output.

Key changes:

• Remove .markdownlint-cli2.yaml, .rubocop.yml, .shellcheckrc, and .yamllint.yml linter configuration files
• Bump Go from 1.26.2 to 1.26.3 (in both go and proto entries in config/languages.yaml)
• Bump Node.js from 25.9.0 to 26.1.0 in config/languages.yaml
• Bump PHP from 8.5.5 to 8.5.6 in config/languages.yaml
• Pin Redis option from latest to 9.0 in config/options/redis.yaml
• Bump multi_xml from 0.9.0 to 0.9.1 in Gemfile.lock
• Add docs/code-review.md to .gitignore

Types of changes

• Bugfix (fixes an issue)
• New feature (adds functionality)
• Refactoring (improves code without changing functionality)
• Breaking change (incompatible changes)
• Build or security update (updates dependencies, libraries, or security patches)
• Code style or documentation update (formatting, renaming, or documentation changes)
• Other (please describe):

Checklist

• Unit tests added to validate my fix/feature
• I have manually tested my change
• I did not add automation test. Why ?: Configuration-only changes (linter config removals, version bumps in YAML configs, gitignore tweak) — no executable code paths to cover.
• Database changes requiring migration with downtime or reprocessing of existing data
• The SOUP file lists the risk Level, requirements and verification reasoning associated with each library
• readme.md includes sections on introduction, installation, usage, and contributing
• docs/architecture.md includes sections on the architecture diagram, software units, software of unknown provenance, critical algorithms and risk controls related to PII and security
• Impact on PII, privacy regulations (CCPA/GDPR/PIPEDA), CIS benchmarks or security (availability/confidentiality/integrity); management must be notified