docs: update comments for ListVoicesRequest

PiperOrigin-RevId: 424942023

google/cloud/texttospeech/v1/cloud_tts.proto

@@ -61,13 +61,13 @@ service TextToSpeech {
 // The top-level message sent by the client for the `ListVoices` method.
 message ListVoicesRequest {
   // Optional. Recommended.
-  // [BCP-47](https://www.rfc-editor.org/rfc/bcp/bcp47.txt) language tag. If
-  // specified, the ListVoices call will only return voices that can be used to
-  // synthesize this language_code. E.g. when specifying `"en-NZ"`, you will get
-  // supported `"en-\*"` voices; when specifying `"no"`, you will get supported
-  // `"no-\*"` (Norwegian) and `"nb-\*"` (Norwegian Bokmal) voices; specifying
-  // `"zh"` will also get supported `"cmn-\*"` voices; specifying `"zh-hk"` will
-  // also get supported `"yue-\*"` voices.
+  // [BCP-47](https://www.rfc-editor.org/rfc/bcp/bcp47.txt) language tag.
+  // If not specified, the API will return all supported voices.
+  // If specified, the ListVoices call will only return voices that can be used
+  // to synthesize this language_code. For example, if you specify `"en-NZ"`,
+  // all `"en-NZ"` voices will be returned. If you specify `"no"`, both
+  // `"no-\*"` (Norwegian) and `"nb-\*"` (Norwegian Bokmal) voices will be
+  // returned.
   string language_code = 1 [(google.api.field_behavior) = OPTIONAL];
 }