ci(windows): reset exit code after accepting untrusted test-cert root

The verify script accepted both signed binaries and printed "verification
passed", but the step still failed: signtool exits 1 on the untrusted test
root, and GitHub's pwsh wrapper exits with that lingering $LASTEXITCODE.
Add an explicit `exit 0` on the success path so the step passes.

scripts/verify-authenticode.ps1

@@ -102,3 +102,8 @@ foreach ($relativePath in $Files) {
 }
 
 Write-Host "Authenticode verification passed."
+
+# signtool exits non-zero for the untrusted test-cert root even when we accept
+# it above, leaving $LASTEXITCODE = 1. The GitHub Actions pwsh wrapper exits
+# with that lingering code, so reset it to report success explicitly.
+exit 0