Bumped manifest to 3.906

<?xml version="1.0" encoding="utf-8"?>

<manifest

    xmlns:android="http://schemas.android.com/apk/res/android"

    android:versionCode="14005"

    android:versionName="3.905" package="com.fsck.k9"

    android:versionCode="14006"

    android:versionName="3.906" package="com.fsck.k9"

    >

    <uses-sdk

       android:minSdkVersion="3"