Fix: rename ms_per_buffer to buffer_duration

Buffer duration is in seconds, not milliseconds.

No-Try: True
Bug: webrtc:11430
Change-Id: Ib03c2002f2dc6c43e01e50d745d709c2644c8b1e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/170500
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30798}
diff --git a/AUTHORS b/AUTHORS
index 64a3e5c..d306c51 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -34,6 +34,7 @@
 Jiawei Ou <jiawei.ou@gmail.com>
 Jie Mao <maojie0924@gmail.com>
 Jose Antonio Olivera Ortega <josea.olivera@gmail.com>
+Kiran Thind <kiran.thind@gmail.com>
 Luke Weber <luke.weber@gmail.com>
 Maksim Khobat <maksimkhobat@gmail.com>
 Mallikarjuna Rao V <vm.arjun@samsung.com>