PySide2: when plotting response, do not plot all previous unprompted

OS: Fedora 36.

Observed behavior: if a response plot is requested, and then later a response plot is requested for another channel, the plot that has just been requested as well as all past response plots appear. The behavior is consistent whether the original plot is still open or not.

Requested behavior: plot only the requested response plot to make consistent with past releases. Alternatively, prompt user they will get n plots.

Priority: recommend low