man: Correct "rate" option

alsa-project/alsa-utils pull request #83 was edited from nootc:

https://github.com/alsa-project/alsa-utils/issues/82 Change "rate" option from "-c" to "-r".

Request URL : https://github.com/alsa-project/alsa-utils/pull/83 Patch URL : https://github.com/alsa-project/alsa-utils/pull/83.patch Repository URL: https://github.com/alsa-project/alsa-utils