Revert "Remove chronos from audio group"

This reverts commit b847cb8114634899da97b25c47f4dfb0c4fc6023.

Reason for revert: It makes Chrome can not access /dev/snd/seq and breaks midi function.

Original change's description:
> Remove chronos from audio group
>
> chronos should use audio devices via CRAS instead of directly accessing
> alsa, so remove it from the audio group.
>
> BUG=chromium:216640
> TEST=Verified that the alsa test in tast and autotest still can be passed.
>
> Cq-Depend: chromium:1824784
> Change-Id: Id07ab690575486ad8679101d1e67fa91127cf31b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/1802062
> Reviewed-by: Shuhei Takahashi <nya@chromium.org>
> Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
> Reviewed-by: Allen Webb <allenwebb@google.com>
> Tested-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
> Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>

BUG=chromium:216640
TEST=audio_Aconnect test pass

Cq-Depend: chromium:1835886
Change-Id: I6cce16f1dc631ce6a336b5091f3cc82ef756f136
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/1837023
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Reviewed-by: Allen Webb <allenwebb@google.com>
Tested-by: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
diff --git a/profiles/base/accounts/group/audio b/profiles/base/accounts/group/audio
index 0f40539..739276b 100644
--- a/profiles/base/accounts/group/audio
+++ b/profiles/base/accounts/group/audio
@@ -1,3 +1,3 @@
 group:audio
 gid:18
-users:cras,volume,midis,rtanalytics
+users:cras,chronos,volume,midis,rtanalytics