sw: Fix SID_CHAR_DLG_EFFECT behavior

A regression from commit f41e7c70. The wrong tab is
opened (used in the sidebar underline popup). The
correct id is "fonteffects" not "fonteffect".

Change-Id: Ic06fb3f93a033bcfe24b97eb124ceea082b4087f
(cherry picked from commit d8d18c3cc707d38d98463ed43ae08e1d6bc6e56f)
Reviewed-on: https://gerrit.libreoffice.org/9854
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>