[5.1.x] Fixed #35443 -- Changed ordinal to return negative numbers unchanged.

Previously, `-1` was converted to `"-1th"`. This has been updated to
return negative numbers "as is", so that for example `-1` is
converted to `"-1"`. This is now explicit in the docs.

Co-authored-by: Martin Jonson <artin.onson@gmail.com>

Backport of d3a7ed5bcc from main.

docs/ref/contrib/humanize.txt

@@ -143,3 +143,4 @@ Examples:
 * ``3`` becomes ``3rd``.
 
 You can pass in either an integer or a string representation of an integer.
+Negative integers are returned unchanged.