Remove settitle

settitle always had a bug in the PROMPT_COMMAND, it used "\033]0;",
where it should be "\033[0m". It was opt-in, and changed to opt-out, and
no one really complained that it didn't work. So we are just going to
remove this.

References:
- http://www.termsys.demon.co.uk/vtansi.htm
- https://en.wikipedia.org/wiki/ANSI_escape_code

Test: lunch and see no change in prompt
Change-Id: I777c87b4d8e80c0e9437e5d2628f6df020883389