inputMethod: Do not change IBus.Capabilite by focus events

gnome-shell calls ibus_input_context_focus_in() in InputMethod.focus_in()
but the event is not actually forwarded to panels and engines in GNOME
Wayland because gnome-shell changes IBus.Capabilite by focus events and
disables IBus.Capabilite.FOCUS when ibus_input_context_focus_in() is called.

IBus.Capabilite is assumed a fixed value per input context in the
first place and it should not be changed by focus events.

GNOME/gnome-shell#573
4 jobs for !232 with ibus-capabilities in 4 minutes and 42 seconds (queued for 1 second)
latest detached
Status Job ID Name Coverage
  Review
passed #273003
check_commit_log

00:00:40

 
  Build
passed #273004
build

00:02:35

 
  Test
passed #273005
test

00:01:26

passed #273006
test-pot

00:01:23