COIL: Remove the use of master

Use host instead.

BUG=b:167649426
TEST=None

Change-Id: I6594cf77dbaf7ff634edf447cd7e600177526710
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/audiotest/+/2820585
Commit-Queue: En-Shuo Hsu <enshuo@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Tested-by: En-Shuo Hsu <enshuo@chromium.org>
Auto-Submit: En-Shuo Hsu <enshuo@chromium.org>
Reviewed-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
diff --git a/README.md b/README.md
index 219c637..d7bd74a 100644
--- a/README.md
+++ b/README.md
@@ -39,7 +39,7 @@
 
 Additional features planned for inclusion very shortly:
 - Automatic test sequencing of multiple channels in a port.
-- Remote control, so a master can test ports in a Device Under Test.
+- Remote control, so a host can test ports in a Device Under Test.
 - Higher resolution sound capture with new hardware.
 
 ## Packages included