Update README to remove outdated information

README said, in the tripleo-image-elements section, that "Full HA
is not yet implemented
https://bugs.launchpad.net/neutron/+bug/1174132" but the bug
seems to be in a "Fix committed" state. So removing those two
lines.

Change-Id: I0f1b057631c6692d38a328b552d6c4a27b3bf393
Merge "Update README to remove outdated information"