keyboard: Reset latched levels on string commit on all situations

keyboard: Reset latched levels on string commit on all situations

The _commitAction() paths have early returns, which made resetting the
latched mode inconsistent depending on the paths taken to commit the
string. This made latched modes not return to normal on e.g. Shell
entries.

Make this happen outside the function, and after the only calling
point, so that the level is correctly reset on all situations.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2945>