fdo#81264 Calc is not accessible to screen readers if sheet is modified [a11y]

When the IA2 changes was merged it removed the call to CommitFocusGained
and thereby stopped sending a STATE_CHANGED FOCUSED. A big thank you to
Joanmarie Diggs for noticing the lack of that event.

I tested the patch on Fedora, Windows and Mac. At a quick glance Windows and Mac seem unaffected by the patch but Fedora and Orca seem to require the added event.

Change-Id: Ic616d1b367ad8b8ed5d243e0ba124764082e96f1
Reviewed-on: https://gerrit.libreoffice.org/11451
Reviewed-by: Eike Rathke <erack@redhat.com>
Tested-by: Eike Rathke <erack@redhat.com>
(cherry picked from commit 93410b5ba13749cf3663d3d696fe1a14474bf696)
Reviewed-on: https://gerrit.libreoffice.org/11544
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>