Filter out static text leaf nodes when assessing if an object is "simple"
Filter out static text leaf nodes when assessing if an object is "simple"

Chromium exposes static text leaf nodes which we try hard to ignore.
The label inference code was failing to ignore them. As a result, some
candidate functional labels were being ignored due to having too many
children.

GNOME/orca,GNOME/orca,GNOME/orca,GNOME/orca