Pasting content does not remove trailing BR tag

[ungue]

Hi.

When you have useLineBreaks option disabled and paste text, a
tag is always appended after the pasted text:

Suppose we have this markup:
<p><br></p>

Then, we paste the text 'Hello':
<p>Hello<br></p>

If we press enter to start a new line, the markup looks as follows:

<p>Hello<br></p>
<p><br></p>

Note the extra br

The desired markup should be:

<p>Hello</p>
<p><br></p>

This PR removes that trailing br when pasting content.