[DOCS-15096] Fix spelling typos in Code Security docs

[melamos]

What does this PR do? What is the motivation?

Fixes DOCS-15096

Fixes 4 spelling typos in the Code Security documentation:

• vulnearability → vulnerability
• Compatiblity → Compatibility
• Vulernabilities → Vulnerabilities
• Rentention → Retention

Merge instructions

Merge readiness:

• Ready for merge

AI assistance

Used Claude Code for the full change: identifying and fixing the typos, running Vale, and creating this PR.

Additional notes

[github-actions]

⚠️ Possible site support note detected

The following files have a site-region shortcode at the top of the page that mentions a feature being "not available" or "not supported":

• content/en/security/code_security/static_analysis/setup/_index.md

Are you trying to document site support for a product? If so, the site-region shortcode is not the recommended approach. See the Documenting site support guide for the preferred method.

[github-actions]

Preview links (active after the build_preview check completes)

Modified Files

• https://docs-staging.datadoghq.com/melissa/fix-code-security-typos/security/code_security/iast/setup/nodejs
• https://docs-staging.datadoghq.com/melissa/fix-code-security-typos/security/code_security/software_composition_analysis/setup_runtime/compatibility/dotnet
• https://docs-staging.datadoghq.com/melissa/fix-code-security-typos/security/code_security/static_analysis/ai_enhanced_sast
• https://docs-staging.datadoghq.com/melissa/fix-code-security-typos/security/code_security/static_analysis/setup/

[datadog-datadog-prod-us1-2]

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⚠️ Warnings

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[melamos]

Closing in favor of a new PR from the renamed branch melissa.amos/fix-code-security-typos.