[7.3.x] Reference "Status of Python Versions" in backwards-compatibility policy (#11010)

Co-authored-by: Ronny Pfannschmidt <[email protected]>

Author: github-actions[bot]

doc/en/backwards-compatibility.rst

@@ -92,3 +92,5 @@ pytest version  min. Python version
 5.0 - 6.1       3.5+
 3.3 - 4.6       2.7, 3.4+
 ==============  ===================
+
+`Status of Python Versions <https://devguide.python.org/versions/>`__.