Revert "Remove GPG signing color"

What does this MR do?

Revert "Remove GPG signing color"

This reverts commit 2b238fce.

Why was this MR needed?

This reverts the changes made in Draft: Pilot runners (!6484 - closed) as a fix has been implemented in Properly escape ANSI color codes in shell scripts (!6527 - merged)

⚠️ Important

This MR cannot be merged until Properly escape ANSI color codes in shell scripts (!6527 - merged) is deployed with the Pilot Runners.

What's the best way to test this MR?

After deployment of Properly escape ANSI color codes in shell scripts (!6527 - merged), all the packages' jobs must pass.

What are the relevant issue numbers?

Relate to step-runner#414 (closed)