New-DbaComputerCertificate - Match the warning text across all warnings of the failed request

(do New-DbaComputerCertificate)

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: andreasjordan

tests/New-DbaComputerCertificate.Tests.ps1

@@ -304,7 +304,8 @@ Describe $CommandName -Tag IntegrationTests {
 
         It "Warns instead of returning a certificate" {
             $unreachableCaResult | Should -BeNullOrEmpty
-            $unreachableCaWarning | Should -Match "Failure when attempting to create the cert"
+            # The command writes several warnings on this path, the last one is the message of Stop-Function.
+            ($unreachableCaWarning -join " ") | Should -Match "Failure when attempting to create the cert"
         }
 
         It "Removes the pending request and its key again" {