I used fromtexttospeech.com/ to create the audio file. I entered the text and selected the Create Audio File button.
I right-clicked on the created file and downloaded it to my computer.
I uploaded it to Google Drive.
In Drive I right-clicked it and set the sharing to anyone with the link can view.
I copied the shared link.
I pasted that link in the Embed insert function.
text to speech.mp3