Update en-GB.com_todo.ini

Installed into fresh J3.2.1

When adding an item in admin area this string appears "COM_TODO_ITEMS_DESCRIPTION_LABEL"
I notice FoF adds it automatically (by convetion) is it not defined in the form.form.xml
Merge pull request #11 from willfaulds/patch-1

Update en-GB.com_todo.ini. Good catch!