deps: update dependency hashicorp/packer to v1.15.0

[renovate]

This PR contains the following updates:

Package	Update	Change
hashicorp/packer	minor	1.14.3 → 1.15.0

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Release Notes

hashicorp/packer (hashicorp/packer)

v1.15.0

Compare Source

IMPROVEMENTS:

• core/hcp: add support for updating HCP Packer registry channels and bucket log UI metadata.
  GH-13532

• build: update Go to 1.24.12.
  GH-13553

• docker: remove vmware and vsphere from the packer full image.
  GH-13442

• docs: add comments to packer docs.
  GH-13534

• compliance: update copyright and license headers.
  GH-13540
  GH-13543
  GH-13545
  GH-13544

BUG FIXES:

• datasource/http: update acceptance test URL to avoid rate limiting.
  GH-13480

• provisioner/powershell: ensure LASTEXITCODE is set before checking its value in tests.
  GH-13539

SECURITY:

• Bump golang.org/x/crypto to 0.46.0
  GH-13546

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