Hi Muzamil,
Currently there is no way to change this location. I would suggest that the other plugins (ant, maven , gradle etc.) are a better fit for generating the reports if you want to browse them outside of an IDE.
In the longer term, the HTML reports will not be generated at all and replaced by a view so it would not be wise to rely on this aspect of the plugins behaviour.
If you really want to look at the reports, you can find it under the eclipse workspace in the location <WORKSPACE>/.metadata/.plugins/org.pitest.pitclipse.core/html_results/
Kind regards,
Phil