Rename test_value_from_datadict to test_example_numbers

Better conveys what it test. Was not changed in previous commit to limit
help tracking moved tests.

tests/test_formfields.py

@@ -189,7 +189,7 @@ class TestForm(forms.Form):
             rendered,
         )
 
-    def test_value_from_datadict(self):
+    def test_example_numbers(self):
         example_numbers = (
             self.example_number("US"),
             self.example_number("CA"),