docs: display helm-diff install syntax for helm 3 or 4

[schmaustech]

This PR shows installation of helm-diff plugin depending on which version of helm being used. If version 4 then --verify=false and if version 3 no need for switch.

Related issues

None

Type of Change

• Add - New feature or capability
• Change - Changes in existing functionality
• [ X] Fix - Bug fixes
• Remove - Removed features or deprecated functionality
• Internal - Internal changes (refactoring, tests, docs, etc.)

Breaking Changes

• This PR contains breaking changes

Testing

• Unit tests added/updated
• Integration tests added/updated
• Manual testing performed
• [ X] No testing required (docs, internal refactor, etc.)

Additional Notes

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🔍 Container Scan Summary

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[github-actions]

🌿 Preview your docs: https://nvidia-preview-pull-request-3135.docs.buildwithfern.com/infra-controller

[coderabbitai]

Walkthrough

This change adds a new "Helm v4" subsection to the quick-start documentation, providing a plugin installation command using --verify=false, placed immediately before the existing "Helm v3" section, which remains unchanged.

Changes

Quick-start documentation update

Layer / File(s)	Summary
Add Helm v4 install section docs/getting-started/quick-start.md	Inserts a new "Helm v4" subsection with a helm plugin install command using --verify=false, placed before the existing "Helm v3" section.

Estimated code review effort: 1 (Trivial) | ~2 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title accurately reflects the docs-only change to Helm diff install syntax for Helm 3 and Helm 4.
Description check	✅ Passed	The description is directly related to the docs update and correctly explains the Helm 3/4 install flag difference.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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