AX: WebSpeech only allows use of selected voices.

https://bugs.webkit.org/show_bug.cgi?id=242588

Reviewed by Andres Gonzalez.

The logic for selecting a voice was ignoring if the a voice had been set already.
No great way to test this since it's about choosing the voice that goes into the synthesizer and there's not a callback for that.

* Source/WebCore/platform/cocoa/PlatformSpeechSynthesizerCocoa.mm:
(-[WebSpeechSynthesisWrapper speakUtterance:]):

Canonical link: https://commits.webkit.org/252346@main

Source/WebCore/platform/cocoa/PlatformSpeechSynthesizerCocoa.mm

@@ -132,7 +132,10 @@ - (void)speakUtterance:(RefPtr<WebCore::PlatformSpeechSynthesisUtterance>&&)utte
         voiceLanguage = utterance->voice()->lang();
 
     AVSpeechSynthesisVoice *avVoice = nil;
-    if (voiceLanguage)
+    if (utteranceVoice)
+        avVoice = [PAL::getAVSpeechSynthesisVoiceClass() voiceWithIdentifier:utteranceVoice->voiceURI()];
+
+    if (!avVoice)
         avVoice = [PAL::getAVSpeechSynthesisVoiceClass() voiceWithLanguage:voiceLanguage];
 
     AVSpeechUtterance *avUtterance = [PAL::getAVSpeechUtteranceClass() speechUtteranceWithString:utterance->text()];