Resolve "Improve build process"

Closes #15 (closed)

android/app/src/debug/AndroidManifest.xml

-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="org.benoitharrault.midisynth">
-    <!-- Flutter needs it to communicate with the running application
-         to allow setting breakpoints, to provide hot reload, etc.
-    -->
+<manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <uses-permission android:name="android.permission.INTERNET"/>
 </manifest>