ci: fix Windows tests silently passing on failure (#2294)

PowerShell doesn't stop on non-zero exit codes by default. `go test`
failures were ignored, and the step reported success because the
subsequent caddy tests passed.

Caught on this job, which fails but is green:
https://github.com/php/frankenphp/actions/runs/23424633971/job/68136742625?pr=2287

.github/workflows/windows.yaml

@@ -229,6 +229,8 @@ jobs:
           $env:PHPRC = Get-Location
 
           go test -race ./...
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
           cd caddy
           go test -race ./...
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
         working-directory: ${{ github.workspace }}\frankenphp