Expansion-panel's animation adds a margin to the host element

[jelbourn]

The expansion-panel uses a margin on the host element for its expansion animation. This goes against out policy of not having margins on host elements. We should refactor this animation to work differently.

[crisbeto]

Resolved by #6546.

[angular-automatic-lock-bot]

This issue has been automatically locked due to inactivity.
Please file a new issue if you are encountering a similar or related problem.

Read more about our automatic conversation locking policy.

_{This action has been performed automatically by a bot.}