[SEC-3551] Update version of the code-sign-action

[petergasper]

Update version of the code-sign-action before upcoming signing key rotation.

Changes:

• Bump version of the code-sign-action.
• Add keypair alias variable which was hard coded in the previous versions.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 77.54%. Comparing base (2e4a2cd) to head (64ac86a).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #154   +/-   ##
=======================================
  Coverage   77.54%   77.54%           
=======================================
  Files           9        9           
  Lines         677      677           
  Branches       38       38           
=======================================
  Hits          525      525           
  Misses        126      126           
  Partials       26       26           

[polomani]

thanks!