Issue #6053 manual test.

The link selection attributes should cleared in certain situations after the link was pasted

1. Copy a part of a link in the content.
2. Paste it a paragraph.

Expected: The link should be pasted but you should be able to type unlinked text right away.

1. Try copying and pasting links in different places:
   1. In the middle of another link.
   2. At the beginning/end of another link.
   3. Using links with different URLs.
   4. When the selection gravity is overridden at the boundary of an existing link (use arrow left and right keys).

Expected: If a pasted link is not followed by another link, you should always be able to type unlinked text right away after pasting. There should be no selection attributes starting with "link".

Tip: If not sure, check the Model/Selection tab in the inspector and look for selection attributes.