Correct the app bar color theme of Digital Assistant app

Fixes: 190450049
Test: visual
Change-Id: Ib3ff19bd8a00060400960fd92060ac7b136fd3d5
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index c4bf977..f6bd6f2 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -712,7 +712,8 @@
         <activity
             android:name="Settings$ManageAssistActivity"
             android:exported="true"
-            android:label="@string/assist_and_voice_input_title">
+            android:label="@string/assist_and_voice_input_title"
+            android:theme="@style/Theme.SubSettings">
             <intent-filter android:priority="1">
                 <action android:name="android.settings.VOICE_INPUT_SETTINGS" />
                 <category android:name="android.intent.category.DEFAULT" />