Update doc/en/backwards-compatibility.rst

Co-authored-by: Bruno Oliveira <[email protected]>

Author: Pierre-Sassoulas

doc/en/backwards-compatibility.rst

@@ -83,7 +83,7 @@ Released pytest versions support all Python versions that are actively maintaine
 ==============  ===================
 pytest version  min. Python version
 ==============  ===================
-9.0+            3.9+
+8.4+            3.9+
 8.0+            3.8+
 7.1+            3.7+
 6.2 - 7.0       3.6+