Fix #5427 - Line not shared across matched axes

- Bug was that function marked the axis to be connected, but the trace_kwargs still had unique axes
- Change: change the keyword argument for the trace, so that when the graph is initialized, it uses the correct axis instead of the autogenerated one
- Note: The program generates a unique axis label for each subgraph, and then overwrites the label (under this fix)

Author: richmanpoorman

plotly/_subplots.py

@@ -926,6 +926,7 @@ def update_axis_matches(first_axis_id, subplot_ref, spec, remove_label):
             else:
                 axis_name = subplot_ref.layout_keys[layout_key_ind]
                 axis_to_match = layout[axis_name]
+                subplot_ref.trace_kwargs[axis_name] = first_axis_id # Changes the reference axis in the set up to the initial axis (the axis to match)
                 axis_to_match.matches = first_axis_id
                 if remove_label:
                     axis_to_match.showticklabels = False
@@ -981,6 +982,7 @@ def update_axis_matches(first_axis_id, subplot_ref, spec, remove_label):
                 first_axis_id = update_axis_matches(
                     first_axis_id, subplot_ref, spec, ok_to_remove_label
                 )
+    
 
 
 def _init_subplot_xy(layout, secondary_y, x_domain, y_domain, max_subplot_ids=None):