use 'density matrix' instead of 'state matrix' in the plotting tutorial

[eliarbel]

the tutorials/circuits/2_plotting_data_in_qiskit.html tutorial uses 'state matrix' when talking about plot_state_city and plot_state_hinton. I think it's better to use 'density matrix' instead; the documentation of those methods also uses density matrix

[fs1132429]

i would like to contribute to this

[shil-m]

Hi @fs1132429, I didn't notice you commented you wanted to work on it, I read the issue earlier but made the PR later without commenting here. I am still figuring out the policies in GitHub. I am not sure what could be done in this case, should I close my PR? @eliarbel Any comments?

[eliarbel]

PR #1196 should suffice, thanks a lot