beckham: Make ModService requires MODIFY_AUDIO_ROUTING permission

* Previous to 11, this permission wasn't explicitely needed.
  Now it is, and ModService doesn't request it, so allow do the
  following:

  * `apktool d ModService.apk`
  * Add the following permission to the list of requested permissions:
    <uses-permission android:name="android.permission.MODIFY_AUDIO_ROUTING"/>
  * `apktool b ModService -o ModService.apk`

* Additionally, this is now fine to platform sign, as Moto Mods are now
  EOL, and therefore we don't have to worry about ModService updates
  anymore. We will leave the vendor_platform_signature function for
  for other apps like ProjectorMod to use.

Change-Id: Ie4a218ff94dc47091487cc0af7a1dd28b79ed863

proprietary-files.txt

@@ -457,7 +457,7 @@ vendor/lib64/libkeymasterutils.so
 
 # Moto Mods
 -priv-app/ModFmwkProxyService/ModFmwkProxyService.apk|37a020b2350748a5f684870d652a1e3e31d8d1e2
--priv-app/ModService/ModService.apk|ac2cfdce29c6e023a600bd96613e270815f3c878
+-priv-app/ModService/ModService.apk|c823ccd189721d1c39ba667e8a7d1151cdf88a8d
 -priv-app/ProjectorApp/ProjectorApp.apk|fd501856dc2f20a78397ef770cfe5f7a73ead9ca
 etc/firmware/upd-00000126-00001001-fed70128-fffe0001-02.tftf
 etc/permissions/com.motorola.aov.xml