Remove noneed plotting code

• remove ax.linkedX because there is no use for it.
• remove zoom_marker2_follow_mouse: we don't let zoom_marker2 to follow mouse anymore because it slow down the performance but have the zoom_marker2 to show up for short time the perform zoom.

sohstationviewer/view/plotting/plotting_widget/plotting.py

@@ -117,10 +117,7 @@ class Plotting:
         self.plotting_axes.set_axes_info(
             ax, [total_samples], sample_no_colors=sample_no_colors,
             chan_db_info=chan_db_info, linked_ax=linked_ax)
-        if linked_ax is None:
-            ax.x = x
-        else:
-            ax.linkedX = x
+        ax.x = x
         ax.chan_db_info = chan_db_info
         return ax
 
@@ -182,10 +179,7 @@ class Plotting:
             sample_no_colors=[clr[colors[0]], clr[colors[1]]],
             sample_no_pos=[0.25, 0.75],
             chan_db_info=chan_db_info, linked_ax=linked_ax)
-        if linked_ax is None:
-            ax.x = x
-        else:
-            ax.linkedX = x
+        ax.x = x
         ax.chan_db_info = chan_db_info
         return ax
 
@@ -225,10 +219,7 @@ class Plotting:
                     linestyle='', zorder=constants.Z_ORDER['LINE'],
                     color=clr[color], picker=True,
                     pickradius=3)
-        if linked_ax is None:
-            ax.x_list = x_list
-        else:
-            ax.linkedX = x_list
+        ax.x_list = x_list
         ax.chan_db_info = chan_db_info
         return ax
 
@@ -313,12 +304,8 @@ class Plotting:
                                     mec=clr[d_color],
                                     picker=True, pickradius=3)
 
-        if linked_ax is None:
-            ax.x_list = x_list
-            ax.y_list = y_list
-        else:
-            ax.linkedX = x_list
-            ax.linkedY = y_list
+        ax.x_list = x_list
+        ax.y_list = y_list
         ax.chan_db_info = chan_db_info
         return ax