Instead of relying on an environment variable
This will also set the other necessary settings that we need for the
session to integrate properly like the Placement strategy for kwin
I wonder why we were specifying maliit-server now, definitely was
unused.
Using maliit-keyboard we'll get to leverage the input-method-v1 support
we have now in kwin, allowing to move the keyboard into a separate
process and making the development of the virtual keyboard increasinly
modular.