Spring-ai Add comment in OpenAiAudioSpeechModel and remove duplicated comment in OpenAiAudioSpeechOptions

• Add comment in OpenAiAudioSpeechModel like OpenAiChatModel
• Remove duplicated word in OpenAiAudioSpeechOptions (AudioResponseFormat comment)

resolved #931

Comment From: markpollack

merged in 3411e3e74d383434fea388b9eef6cd537d1266f8