Use the new, official digicert action

[rozyczko]

Description

New windows signing action implemented

Fixes #3925

How Has This Been Tested?

Will be tested with the installer

Review Checklist:

[if using the editor, use [x] in place of [ ] to check a box]

Documentation (check at least one)

• [ X] There is nothing that needs documenting
• Documentation changes are in this PR
• There is an issue open for the documentation (link?)

Installers

• [ X] There is a chance this will affect the installers, if so
  • [X ] Windows installer (GH artifact) has been tested (installed and worked)
  • MacOSX installer (GH artifact) has been tested (installed and worked)
  • Wheels installer (GH artifact) has been tested (installed and worked)

Licensing (untick if necessary)

• The introduced changes comply with SasView license (BSD 3-Clause)

[rozyczko]

This seems to work fine as seen in https://github.com/SasView/sasview/actions/runs/25228263991/artifacts/6755195244

[krzywon]

The installer file you linked to was signed and ran as expected.