fix default gather input is digits and gather dtmf should not require speech

lib/tasks/stt-task.js

@@ -110,7 +110,12 @@ class SttTask extends Task {
       this.data.recognizer.model = cs.speechRecognizerLanguage;
     }
 
-    if (!this.sttCredentials) {
+    if (
+      // not gather task, such as transcribe
+      (!this.input ||
+      // gather task with speech
+        this.input.includes('speech')) &&
+      !this.sttCredentials) {
       try {
         this.sttCredentials = await this._initSpeechCredentials(this.cs, this.vendor, this.label);
       } catch (error) {