Don't write a anti-aliasing settings from startkde

Summary:
Writing a config files in $HOME at start-up is wrong way of setting
defaults, If defaults needs to be set, they should be set by krdb
instead of the startkde.

Another side-effect of writing config file is that this breaks the
distribution/vendor configuration, who might want to configure this
value by shipping kdeglobals in either /etc/xdg or $XDG_CONFIG_DIRS.

BUG: 407754
CCBUG: 389598

Reviewers: #plasma, ngraham, apol, davidedmundson

Reviewed By: #plasma, ngraham, apol, davidedmundson

Subscribers: apol, ngraham, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D21335