doc: Remove attrs from __repr__ changes

Address comment from @keewis:
`.attrs` is a standard python dict, so there's no custom repr.

doc/whats-new.rst

@@ -27,10 +27,10 @@ New Features
 Breaking changes
 ~~~~~~~~~~~~~~~~
 
-- The ``__repr__`` of a :py:class:`xarray.Dataset`'s ``attrs``, ``coords``,
-  and ``data_vars`` ignore ``xarray.set_option(display_max_rows=...)`` and
-  show the full output when called directly as, e.g., ``ds.data_vars`` or
-  ``print(ds.data_vars)`` (:issue:`5545`, :pull:`5580`).
+- The ``__repr__`` of a :py:class:`xarray.Dataset`'s ``coords`` and ``data_vars``
+  ignore ``xarray.set_option(display_max_rows=...)`` and show the full output
+  when called directly as, e.g., ``ds.data_vars`` or ``print(ds.data_vars)``
+  (:issue:`5545`, :pull:`5580`).
   By `Stefan Bender <https://github.com/st-bender>`_.
 
 Deprecations