todo widget: Downgrade error to warning.
todo widget: Downgrade error to warning.

We were creating errors for task keys that were
from older versions of the widget.  We don't migrate
data for the widgets yet (they're all still considered
to be somewhat beta); instead, we just drop bad data
on the floor.

Rohitt and I re-tested the widget on czo pretty
extensively to verify that these errors don't show
up for newly created widgets.

kou/zulip,andersk/zulip,punchagan/zulip,showell/zulip,punchagan/zulip,kou/zulip,timabbott/zulip,andersk/zulip,showell/zulip,zulip/zulip,rht/zulip,showell/zulip,zulip/zulip,synicalsyntax/zulip,eeshangarg/zulip,brainwane/zulip,eeshangarg/zulip,eeshangarg/zulip,hackerkid/zulip,andersk/zulip,brainwane/zulip,rht/zulip,rht/zulip,brainwane/zulip,kou/zulip,shubhamdhama/zulip,zulip/zulip,kou/zulip,synicalsyntax/zulip,brainwane/zulip,hackerkid/zulip,shubhamdhama/zulip,zulip/zulip,rht/zulip,andersk/zulip,zulip/zulip,synicalsyntax/zulip,zulip/zulip,showell/zulip,shubhamdhama/zulip,showell/zulip,punchagan/zulip,shubhamdhama/zulip,punchagan/zulip,showell/zulip,synicalsyntax/zulip,eeshangarg/zulip,eeshangarg/zulip,hackerkid/zulip,kou/zulip,brainwane/zulip,hackerkid/zulip,brainwane/zulip,synicalsyntax/zulip,timabbott/zulip,andersk/zulip,synicalsyntax/zulip,eeshangarg/zulip,showell/zulip,shubhamdhama/zulip,kou/zulip,timabbott/zulip,timabbott/zulip,hackerkid/zulip,shubhamdhama/zulip,eeshangarg/zulip,andersk/zulip,rht/zulip,brainwane/zulip,hackerkid/zulip,zulip/zulip,shubhamdhama/zulip,rht/zulip,andersk/zulip,kou/zulip,timabbott/zulip,synicalsyntax/zulip,timabbott/zulip,punchagan/zulip,hackerkid/zulip,rht/zulip,punchagan/zulip,timabbott/zulip,punchagan/zulip