fix(tracking): Opt out of webview metric collection

Author: pixincreate

app/src/main/AndroidManifest.xml

@@ -116,6 +116,10 @@
     <meta-data android:name="google_analytics_adid_collection_enabled" android:value="false" />
     <meta-data android:name="firebase_messaging_auto_init_enabled" android:value="false" />
 
+    <!-- PiX: added. This is currently only relevant for captchas. -->
+    <meta-data android:name="android.webkit.WebView.MetricsOptOut"
+        android:value="true" />
+
     <activity android:name=".WebRtcCallActivity"
               android:theme="@style/TextSecure.DarkTheme.WebRTCCall"
               android:excludeFromRecents="true"