Steps to reproduce:

1. On the clean 3.1.0-ee install create a new article.
2. Copy a text paragraph from any PDF/Word document that contains the bold text.
3. Try to unbold text in the pasted paragraph in the Online Editor.

Expected result:

The selected text is unbolded

Actual result:

The selected text is still bold

Most likely it is caused by the fact that `b` tag is used for the pasted text instead of `strong`:

<p data-ez-node-initialized="true">Test&nbsp;
  <b data-stringify-type="bold" data-ez-node-initialized="true">test test&nbsp;</b>test
</p>

Instead of

<p data-ez-node-initialized="true">Test&nbsp;
  <strong data-ez-node-initialized="true">test test&nbsp;</strong>test
</p>