Fix 2 typos

Summary: There is 2 instances of instabnce

Test Plan:
none, this will totally regress ;)

But maybe teaching Krazy2 to read QML comments would help

Reviewers: ngraham, bshah

Reviewed By: ngraham, bshah

Subscribers: plasma-devel

Tags: Kirigami

Differential Revision: https://phabricator.kde.org/D17552