Drop resize animation when adding pages
Summary: It's a bit glitchy and looks a bit odd
Test Plan:
Current: https://youtu.be/pUjmqis9E-w
NoAnimations: https://youtu.be/iqQfkOhObBE
Reviewers: Kirigami, mart
Reviewed By: mart
Subscribers: jensreuterberg, colomar, plasma-devel
Tags: Kirigami
Differential Revision: https://phabricator.kde.org/D3538