remove unused variable

Author: bresch

autotune/autotune.py

@@ -62,7 +62,6 @@ def __init__(self, parent=None):
         self.closed_loop_ref = None
         self.closed_loop_ax = None
         self.bode_plot_ref = None
-        self.state_plot_refs= []
         self.pz_plot_refs= []
         self.file_name = None
         self.is_system_identified = False
@@ -184,7 +183,6 @@ def reset(self):
         self.input_ref = None
         self.closed_loop_ref = None
         self.bode_plot_ref = None
-        self.state_plot_refs= []
         self.pz_plot_refs= []
         self.is_system_identified = False