chore(deps): update dependency packer to v1.15.4

[csautter]

This PR contains the following updates:

Package	Update	Change
packer (source)	patch	1.15.3 → 1.15.4

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Release Notes

hashicorp/packer (packer)

v1.15.4

Compare Source

DEPRECATIONS:

• hcp/sbom: removed Syft binary download and handling from the HCP SBOM provisioner; Syft binary management is now deprecated in favor of the native flow.
  GH-13636

BUG FIXES:

• security: addressed authorization-bypass related issues by upgrading go-git and golang.org/x/crypto.
  GH-13645
• sbom: bump CycloneDX dependency to improve BOM generation handling.
  GH-13638

DEPENDENCIES:

• deps: bump github.com/hashicorp/packer-plugin-sdk to v0.6.9.
  GH-13640
• deps: update github.com/Azure/go-ntlmssp to v0.1.1.
  GH-13622
• deps: update go-git and golang.org/x/crypto.
  GH-13645
• build/deps: bump GitHub Actions dependencies group (7 updates).
  GH-13649

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