Fix InlineMessage actions always being placed in overflow menu

Summary:
Due to some of the recent ActionToolBar work, InlineMessage ended up always placing its
actions into the overflow menu. This fixes that.

Test Plan:
Kirigami2Gallery's Inline Messages page now properly shows the actions for messages. When
the window width is reduced, the actions will first be placed on a second line, then moved
to the overflow menu once even that is too little space.

Reviewers: Kirigami, mart

Reviewed By: Kirigami, mart

Subscribers: plasma-devel

Tags: Kirigami

Differential Revision: https://phabricator.kde.org/D25570