repo.bash: replace with better version

From https://raw.github.com/aartamonau/repo.bash_completion/master/repo.bash_completion

Change-Id: I7ca5d7eba70244d875c48ce76c999c8a10b88934
Fix Straight Talk T-mobile APN

Per CYAN-679, MMSC url is incorrect. Adjust accordingly

Change-Id: I9d9f76b4a35f8df44835ea68ff17f356d19c6f8a