Bump version to 3.20.4

// FREEBIE

Author: moxie0

AndroidManifest.xml

@@ -2,8 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
           xmlns:tools="http://schemas.android.com/tools"
           package="org.thoughtcrime.securesms"
-      android:versionCode="206"
-      android:versionName="3.20.3">
+      android:versionCode="207"
+      android:versionName="3.20.4">
 
     <uses-sdk tools:overrideLibrary="com.amulyakhare.textdrawable,com.astuetz.pagerslidingtabstrip,pl.tajchert.waitingdots,com.h6ah4i.android.multiselectlistpreferencecompat"/>