[pgAdmin4][runtime][patch]: Fix for RM#2679

Hi,

Please find attached patch to fix RM#2679.

*Issue:-*
Getting started links does not open second time from "Dashboard" panel if
User close runtime tab and open any URL again.

*Analysis:-*
As in runtime Qt application, when user defined "target=_new" then
"createWindow" signal is called but when user close that new windows and
again click on link then "createWindow" signal is not getting called so
from user point view nothing will happen.

*Solution:-*
To make it work in both runtime and web application, changed "target"
attribute to "_blank" so that "createWindow" signal will be called every
time when user click on any link.

Do review it and let me know for comments.

Thanks,
Neel Patel