Remove setUpClass from Iris tests. (SciTools#4927)

* remove IrisTest.setUpClass

* whatsnew

Author: rcomer

docs/src/whatsnew/latest.rst

@@ -79,7 +79,8 @@ This document explains the changes made to Iris for this release
 💼 Internal
 ===========
 
-#. N/A
+#. `@rcomer`_ removed the obsolete ``setUpClass`` method from Iris testing.
+   (:pull:`4927`)
 
 
 .. comment

lib/iris/tests/__init__.py

@@ -213,11 +213,6 @@ class IrisTest_nometa(unittest.TestCase):
 
     _assertion_counts = collections.defaultdict(int)
 
-    @classmethod
-    def setUpClass(cls):
-        # Ensure that the CF profile if turned-off for testing.
-        iris.site_configuration["cf_profile"] = None
-
     def _assert_str_same(
         self,
         reference_str,