fix(examples) remove cast in MP scripts (#2354)

After https://github.com/lvgl/lv_binding_micropython/pull/161 merged, it is no longer needed to cast the result of 'e.get_target()'

Also, additional small fixes to allow CI improvements

examples/widgets/bar/lv_example_bar_6.py

@@ -6,7 +6,7 @@ def event_cb(e):
     if dsc.part != lv.PART.INDICATOR:
         return
 
-    obj= lv.bar.__cast__(e.get_target())
+    obj= e.get_target()
 
     label_dsc = lv.draw_label_dsc_t()
     label_dsc.init()