Shift-enter in single line editables introduces <p> tags! (regression)

[bago]

Since we moved to "

" based editing for singleline editable (headings, buttons, etc) tinymce behaviour for enter works as before (insert a
) but shift-enter, that previously did nothing, now inserts

tags inside that element and we don't want

tags in single line elements.

Sounds like a bug from tinymce as

are not in the allowed elements, but maybe we can add some workaround to restore the old behaviour.