[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.

tests/humanize_tests/tests.py

@@ -55,6 +55,9 @@ class HumanizeTests(SimpleTestCase):
             "102",
             "103",
             "111",
+            "-0",
+            "-1",
+            "-105",
             "something else",
             None,
         )
@@ -70,6 +73,9 @@ class HumanizeTests(SimpleTestCase):
             "102nd",
             "103rd",
             "111th",
+            "0th",
+            "-1",
+            "-105",
             "something else",
             None,
         )