json syntax error with escaped single quotes

visualeditor-dialog-meta-settings-newsectioneditlink-default message has
an escaped single quote which PHP json_decode() complains about with a
syntax error.  Since the string is between double quotes, I am removing
the backslash and PHP json_decode() is happy again.

You can try it using the PHP based linter in integration/jenkins.git
as bin/json-lint.php

Bug: 58279
Change-Id: Ife1e4723ba9e65b351d65a8691f4c8b8126cc867