Remove some more compatibility code for old pytest (versions < 6)

Author: takluyver

nbval/plugin.py

@@ -344,13 +344,9 @@ def collect(self):
                 options.update(comment_opts)
                 options.setdefault('check', self.compare_outputs)
                 name = 'Cell ' + str(cell_num)
-                # https://docs.pytest.org/en/stable/deprecations.html#node-construction-changed-to-node-from-parent
-                if hasattr(IPyNbCell, "from_parent"):
-                    yield IPyNbCell.from_parent(
-                        self, name=name, cell_num=cell_num, cell=cell, options=options
-                    )
-                else:
-                    yield IPyNbCell(name, self, cell_num, cell, options)
+                yield IPyNbCell.from_parent(
+                    self, name=name, cell_num=cell_num, cell=cell, options=options
+                )
 
                 # Update 'code' cell count
                 cell_num += 1