docs(contributing): update references to reflect AWS CDK CLI is in a separate repo

[jasdeepbhalla]

Issue # (if applicable)

Closes #36220.

Reason for this change

The AWS CDK CLI was moved to a separate repository (aws/aws-cdk-cli) in #32775. But multiple documentation files in this repository still reference the CLI as if it lives here, which can be confusing for contributors and users.

This change updates the documentation to accurately reflect the current repository layout and directs contributors to the correct location for CLI development, testing, and installation.

Description of changes

• Updated CONTRIBUTING.md to remove or clarify CLI-specific development and integration test instructions that no longer apply to this repository.
• Updated MANUAL_INSTALLATION.md to explicitly state that the AWS CDK CLI is released and maintained in the aws/aws-cdk-cli repository.
• Added clear references and links to the CLI repository where appropriate to reduce contributor confusion.

These changes ensure documentation consistency after the CLI repository split and improve onboarding for new contributors.

No alternative approaches were considered, as this is a straightforward documentation correction aligning with the current project structure.

Describe any new or updated permissions being added

None.

This is a documentation-only change and does not introduce or modify any IAM
permissions.

Description of how you validated changes

• Manually reviewed the updated documentation to ensure references to the CLI are accurate and consistent.
• Verified that all links to the aws/aws-cdk-cli repository are correct and accessible.
• Confirmed that no build, tooling, or runtime behavior is affected by these changes.

Checklist

• My code adheres to the CONTRIBUTING GUIDE and DESIGN GUIDELINES

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By submitting this pull request, I confirm that my contribution is made under the terms of the Apache-2.0 license

[jasdeepbhalla]

@mrgrain Thanks for the review. I have updated the code with your suggestions.

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

[mergify]

Merge Queue Status

✅ The pull request has been merged at 07a975d

This pull request spent 28 minutes 54 seconds in the queue, including 28 minutes 45 seconds running CI.
The checks were run in-place.

Required conditions to merge

• #approved-reviews-by >= 1 [🛡 GitHub branch protection]
  • docs(contributing): update references to reflect AWS CDK CLI is in a separate repo #36542
• #changes-requested-reviews-by = 0 [🛡 GitHub branch protection]
  • docs(contributing): update references to reflect AWS CDK CLI is in a separate repo #36542
• any of [🛡 GitHub branch protection]:
  • check-success = validate-pr
  • check-neutral = validate-pr
  • check-skipped = validate-pr
• any of [🛡 GitHub branch protection]:
  • check-success = build
  • check-neutral = build
  • check-skipped = build

[mergify]

Thank you for contributing! Your pull request will be updated from main and then merged automatically (do not update manually, and be sure to allow changes to be pushed to your fork).

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