Android: Remove playlist migration logic

It malfunctioned when the game ZIP contained playlist.txt.

Fixes #36.

android/app/src/main/java/io/github/kichikuou/system3/Launcher.kt

@@ -46,7 +46,6 @@ class Launcher private constructor(private val rootDir: File) {
     companion object {
         const val TITLE_FILE = "title.txt"
         const val PLAYLIST_FILE = "playlist2.txt"
-        const val OLD_PLAYLIST_FILE = "playlist.txt"
 
         fun getInstance(rootDir: File): Launcher {
             if (gLauncher == null) {
@@ -118,7 +117,6 @@ class Launcher private constructor(private val rootDir: File) {
                 val titleFile = File(path, TITLE_FILE)
                 val title = titleFile.readText()
                 games.add(Entry(path, title, titleFile.lastModified()))
-                migratePlaylist(path)
             } catch (e: IOException) {
                 // Incomplete game installation. Delete it.
                 path.deleteRecursively()
@@ -198,20 +196,6 @@ class Launcher private constructor(private val rootDir: File) {
         configWriter.write(outDir)
     }
 
-    // System3-sdl2 <=0.7.0 had a bug where playlist had an extra empty line at
-    // the beginning of the file. This migrates playlist.txt created by an old
-    // version of system3-sdl2 to playlist2.txt.
-    private fun migratePlaylist(dir: File) {
-        val oldPlaylist = File(dir, OLD_PLAYLIST_FILE)
-        if (!oldPlaylist.exists())
-            return
-        var tracks = oldPlaylist.readLines()
-        if (tracks.isNotEmpty())
-            tracks = tracks.subList(1, tracks.size)
-        File(dir, PLAYLIST_FILE).writeText(tracks.joinToString("\n"))
-        oldPlaylist.delete()
-    }
-
     class InstallFailureException(val msgId: Int) : Exception()
 
     // A helper class which generates playlist.txt in the game root directory.