Fix typo in Tabs doc.
Fix typo in Tabs doc.

I don't know enough about grammar to say why the "ing" suffix is
correct, but I'm reasonably sure it is :)

(cherry picked from commit 3826f3348f94b03c043bf189d932d15136ae12e3)

ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot,ex/godot