ci: Use Go backports PPA

Author: adombeck

.github/workflows/build-deb.yaml

@@ -69,6 +69,10 @@ jobs:
                 cargo-vendor-filterer@${{ env.CARGO_VENDOR_FILTERER_VERSION }}
               command -v cargo-vendor-filterer
             fi
+            # Install Go 1.25 from our Go backports PPA
+            sudo add-apt-repository ppa:ubuntu-enterprise-desktop/golang
+            sudo apt-get update -y
+            sudo apt-get install -y golang-1.25
 
         # FIXME: Use dynamic outputs when possible: https://github.com/actions/runner/pull/2477
       - name: Generate outputs