EPMDEDP-17274: chore: Bump edp-install chart to 3.15.0

[AlexeyGol]

Upgrade the edp-install dependency to 3.15.0 to pick up upstream changes, including removal of the deprecated edp-headlamp sub-chart and a new Tekton Reporter option to control whether failed-step log lines are published in PR comments.

Pull Request Template

Description

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Fixes #(issue)

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Enhancement (non-breaking change which improves an existing feature or documentation)
• Breaking change (fix or feature that would cause existing functionality not to work as expected)

How Has This Been Tested?

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Checklist:

• I have performed a self-review of my code
• I have commented on my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
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• Pull Request contains one commit. I squash my commits.

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