fix formatting in whatsnew and add issue number to tests

Author: louispotok

doc/source/whatsnew/v0.24.0.txt

@@ -131,7 +131,7 @@ Datetimelike
 
 - Fixed bug where two :class:`DateOffset` objects with different ``normalize`` attributes could evaluate as equal (:issue:`21404`)
 - Bug in :class:`Index` with ``datetime64[ns, tz]`` dtype that did not localize integer data correctly (:issue:`20964`)
-- Fixed bug where `describe` method on tz-aware datetimes did not show `first` and `last` result (:issue:`21328`)
+- Fixed bug where :meth:`DataFrame.describe` and :meth:`Series.describe` on tz-aware datetimes did not show `first` and `last` result (:issue:`21328`)
 
 Timedelta
 ^^^^^^^^^

pandas/tests/frame/test_analytics.py

@@ -418,6 +418,7 @@ def test_describe_timedelta_values(self):
         assert repr(res) == exp_repr
 
     def test_describe_tz_values(self, tz_naive_fixture):
+        # GH 21332
         tz = tz_naive_fixture
         s1 = Series(range(5))
         start = Timestamp(2018, 1, 1)

pandas/tests/series/test_analytics.py

@@ -337,6 +337,7 @@ def test_describe(self):
         tm.assert_series_equal(result, expected)
 
     def test_describe_with_tz(self, tz_naive_fixture):
+        # GH 21332
         tz = tz_naive_fixture
         name = tz_naive_fixture
         start = Timestamp(2018, 1, 1)