Disable SDL codesign auto-scan on the package job (#40657)
The Guardian CodeSign post-analysis scans the entire source checkout and flags every in-repo .ps1 as unsigned (17 errors, breaking the release build). Two prior attempts to filter the findings via the documented ob_sdl_codeSignValidation_excludes variable - at pipeline-level (b011cf77) and at the package job's variables block (PR #40653) - were both silently ignored. Disable the auto-scan on the package job; the msixbundle and nupkg outputs are explicitly signed AND verified by the EsrpCodeSigning tasks in the same job (SigntoolVerify / NuGetVerify operations), so signing coverage on the actual release artifacts is preserved. The build_x64 / build_arm64 jobs keep codesign validation enabled. Co-authored-by: Ben Hillis <benhill@ntdev.microsoft.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>