init.encore.rc: remove obsolete ro.debuggable=1 trigger

Whatever purpose this trigger once served is now handled by the
init.encore.usb.rc triggers introduced in ICS, and keeping it appears to
tickle an init bug concerning /dev/socket sockets handling and
restarting of already-started services.

Fixes log spam of the form:

E/UsbDebuggingManager( 1562): Communication error:
E/UsbDebuggingManager( 1562): java.io.IOException: No such file or directory
E/UsbDebuggingManager( 1562): 	at android.net.LocalSocketImpl.connectLocal(Native Method)
E/UsbDebuggingManager( 1562): 	at android.net.LocalSocketImpl.connect(LocalSocketImpl.java:238)
E/UsbDebuggingManager( 1562): 	at android.net.LocalSocket.connect(LocalSocket.java:108)
E/UsbDebuggingManager( 1562): 	at com.android.server.usb.UsbDebuggingManager.listenToSocket(UsbDebuggingManager.java:79)
E/UsbDebuggingManager( 1562): 	at com.android.server.usb.UsbDebuggingManager.run(UsbDebuggingManager.java:115)
E/UsbDebuggingManager( 1562): 	at java.lang.Thread.run(Thread.java:856)

which may have been a symptom of a memory leak in system_server.