Add title and change spelling for use of approx with non-numerics (#13343)

* Added title to draw attention to the easily-missed information on non-numeric types for approx.
* Changed spelling of all cases of "nonnumeric" to "non-numeric" within docstrings for clarity and consistency with .rst files.

Related to #13218

Author: callummscott

src/_pytest/python_api.py

@@ -632,8 +632,10 @@ def approx(expected, rel=None, abs=None, nan_ok: bool = False) -> ApproxBase:
         >>> 1 + 1e-8 == approx(1, rel=1e-6, abs=1e-12)
         True
 
-    You can also use ``approx`` to compare nonnumeric types, or dicts and
-    sequences containing nonnumeric types, in which case it falls back to
+    **Non-numeric types**
+
+    You can also use ``approx`` to compare non-numeric types, or dicts and
+    sequences containing non-numeric types, in which case it falls back to
     strict equality. This can be useful for comparing dicts and sequences that
     can contain optional values::
 
@@ -708,10 +710,10 @@ def approx(expected, rel=None, abs=None, nan_ok: bool = False) -> ApproxBase:
 
     .. versionchanged:: 3.7.1
        ``approx`` raises ``TypeError`` when it encounters a dict value or
-       sequence element of nonnumeric type.
+       sequence element of non-numeric type.
 
     .. versionchanged:: 6.1.0
-       ``approx`` falls back to strict equality for nonnumeric types instead
+       ``approx`` falls back to strict equality for non-numeric types instead
        of raising ``TypeError``.
     """
     # Delegate the comparison to a class that knows how to deal with the type

testing/python/approx.py

@@ -939,7 +939,7 @@ def test_nonnumeric_okay_if_equal(self, x):
         ],
     )
     def test_nonnumeric_false_if_unequal(self, x):
-        """For nonnumeric types, x != pytest.approx(y) reduces to x != y"""
+        """For non-numeric types, x != pytest.approx(y) reduces to x != y"""
         assert "ab" != approx("abc")
         assert ["ab"] != approx(["abc"])
         # in particular, both of these should return False