Paragraphs in editors are missing spacing

[kewisch]

Describe the bug
When you write something in a ck editor, e.g. conference description, there is no visible difference between a line break and a paragraph. When you view it in the result, there is however. This is mildly confusing.

To Reproduce
Steps to reproduce the behavior:

1. Create an event with a description. Add some text, a few line breaks, a paragraph
2. Save the description
3. Compare what you see in the editor with the final result

Expected behavior
Paragraph spacing in the editor

Screenshots

Additional context
This apparently goes back to this change 1541785 for IE, which I guess we could revert? At the very least, removing that CSS rule will make it default to semantic-ui's 1em margin-bottom.

[ThiefMaster]

Yes I think that commit could be reverted - it was probably used for the legacy registration form which no longer exists anyway..