tests: Update dataset __repr__ tests [1/2]

Updates the dataset `__repr__` test to assure that the dataset output
honours the `display_max_rows` setting, not the `data_vars` output.

Discussed in pydata#5545

xarray/tests/test_formatting.py

@@ -525,7 +525,7 @@ def test__mapping_repr(display_max_rows, n_vars, n_attr):
     with xr.set_options(display_max_rows=display_max_rows):
 
         # Parse the data_vars print and show only data_vars rows:
-        summary = formatting.data_vars_repr(ds.data_vars).split("\n")
+        summary = formatting.dataset_repr(ds).split("\n")
         summary = [v for v in summary if long_name in v]
 
         # The length should be less than or equal to display_max_rows: