The logic to Paint fit parameters for TGraph was not following the (#7854)
The logic to Paint fit parameters for TGraph was not following the (#7854)

one implemented for histogram. the `v` field described here: https://root.cern/doc/master/classTStyle.html#aedeb1d117d9f16af9f8ad430bf956d64
was not working the same way. This PR implement the same behavior for TGraph.
olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root