Previously, there was an issue where the zero width space that was
removed by linkify wasn't also removed by gr-editable-content. This
meant that if a commit message with R= was edited, the zero-width space
would be inserted in the actual commit message.
This change removes the zero width space when editing the content in the
same way that gr-linked-text does.
Bug: Issue 5472
Change-Id: Ia115c7f57da0c81de5cd3c9e6a749922fe0a1ff9
b3cb869c16