[devtools] qunit: only start firefox once per test The separate profile initialization step doesn't seem necessary anymore. This was due to the system-wide installation of the "Sage" Firefox extensions which breaks -url on a fresh profile. Removing this obnoxious extension allows us to launch Firefox in a standard way. Related to #5533333.

Latest changes 
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* table of `all latest changes`_

Links below is providing useful RQL query example.

.. _all latest changes: ../view?rql=Any+M%2CX+WHERE+X+modification_date+M+ORDERBY+M+DESC+LIMIT+30