Fixed documentation on Todoist filtering syntax
Fixed documentation on Todoist filtering syntax

The documentation example mentions filtering by priority with `!p1`.
This used to be the case, but Todoist has dropped the exclamation mark a while ago for this filter.
`./todoist list -f '(overdue | today) & !p1'` also shoes other priorities than `p1`.
`./todoist list -f '(overdue | today) & p1'` filters correctly.
sachaos/todoist,sachaos/todoist