Panel: Remove inline height from .ui-panel-dismiss on _closePanel

Not removing the height from .ui-panel-dismiss breaks the layout if the
page height is changed dynamically once the panel has open and closed
once.

Closes gh-7308
Closes gh-7313
Fixes gh-7312
Panel: Ensure height is removed from modal inline style upon panel close

Tests 6201c906c24d8d67b5dae029731926785c9cb357