Fix a bug/typo in WebRtcSpl_FilterAR which updates the wrong state vector

Bug: webrtc:10877
Change-Id: I089ac68d71a31914ddb020cb78a44295230cb44b
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/149028
Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org>
Commit-Queue: Henrik Lundin <henrik.lundin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28868}
diff --git a/common_audio/signal_processing/filter_ar.c b/common_audio/signal_processing/filter_ar.c
index 2471cd1..b1f666d 100644
--- a/common_audio/signal_processing/filter_ar.c
+++ b/common_audio/signal_processing/filter_ar.c
@@ -87,7 +87,7 @@
         for (i = 0; i < x_length; i++)
         {
             state[state_length - x_length + i] = filtered[i];
-            state[state_length - x_length + i] = filtered_low[i];
+            state_low[state_length - x_length + i] = filtered_low[i];
         }
     }