Revert "Enable detached catalog signing for PyManager index files"

[hugovk]

Reverts #366.

The 3.14.5rc1 Windows build is failing in two places:

"C:\Users\VssAdministrator\.dotnet\tools\sign.exe" code artifact-signing -v Information -fd sha256 -t http://timestamp.acs.microsoft.com/ -td sha256 -ase "***" -asa "pythondev" -ascp "CPython" -act azure-cli -d "Python 3.14.5rc1" "D:\a\1\b\win32\en-us\launcher.msi" || "C:\Users\VssAdministrator\.dotnet\tools\sign.exe" code artifact-signing -v Information -fd sha256 -t http://timestamp.acs.microsoft.com/ -td sha256 -ase "***" -asa "pythondev" -ascp "CPython" -act azure-cli -d "Python 3.14.5rc1" "D:\a\1\b\win32\en-us\launcher.msi" || "C:\Users\VssAdministrator\.dotnet\tools\sign.exe" code artifact-signing -v Information -fd sha256 -t http://timestamp.acs.microsoft.com/ -td sha256 -ase "***" -asa "pythondev" -ascp "CPython" -act azure-cli -d "Python 3.14.5rc1" "D:\a\1\b\win32\en-us\launcher.msi"
  fail: Sign.Core.ISigner[0]
        Please run 'az login' to set up account

https://dev.azure.com/Python/cpython/_build/results?buildId=169868&view=logs&j=519a03d8-671d-5755-c5bb-7c12049216dc&t=5002fbf4-58c4-5c0d-2ccc-771f499e25e7&s=0b9c4c88-e943-5ab8-0b0f-3d823fab818a

And:

##[error]Lost a race with another publish step!

https://dev.azure.com/Python/cpython/_build/results?buildId=169868&view=logs&j=01276e55-d780-56d9-c399-140f656b1651&t=aed6f6ba-86c8-547d-90f1-5c22bf55ef34&s=0b9c4c88-e943-5ab8-0b0f-3d823fab818a

The first is more obviously related to #366. Looks like the second as well, due to a removed if guard.

cc @zooba

[hugovk]

Will merge to continue the release.