Fix bpo-39416: Change "Numeric" to lower case; an english word, not a class name (GH-22867)


This is a trivial fix to [bpo-39416](), which didn't come up until it was already committed

```
Change "Numeric" to "numeric".

I believe this is trivial enough to not need an issue or a NEWS entry, although
I'm unclear on what branches the original pull request received backports.
```

Automerge-Triggered-By: GH:merwok
(cherry picked from commit f8b1ccd63c94bcde1c15d56d24add89861b6ceee)

Co-authored-by: kpinc <kop@karlpinc.com>
diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst
index c0e7edb..5ecf543 100644
--- a/Doc/reference/datamodel.rst
+++ b/Doc/reference/datamodel.rst
@@ -187,7 +187,7 @@
    related to mathematical numbers, but subject to the limitations of numerical
    representation in computers.
 
-   The string representations of the Numeric classes, computed by
+   The string representations of the numeric classes, computed by
    :meth:`__repr__` and :meth:`__str__`, have the following
    properties: