assistant: guard voice match setting ui with flag

The settings ui should only show when feature is enabled.
Also hide the "delete" button for now per ux request.

Bug: b:123254533
Test: locally build and run
Change-Id: Ice44a9888b2d02f901206518967aea2d7bdb43a4
Reviewed-by: Steven Bennetts <>
Commit-Queue: Xiaohui Chen <>
Cr-Original-Commit-Position: refs/heads/master@{#626283}(cherry picked from commit 9531fa203126c6a581eac8cd9702093f30f2e564)
Reviewed-by: Xiaohui Chen <>
Cr-Commit-Position: refs/branch-heads/3683@{#187}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
3 files changed