ci: bump Python matrix up to 3.13

Python below 3.9 are deprecated.

Link: https://devguide.python.org/versions/
Signed-off-by: Ariel Otilibili <[email protected]>

Author: ariel-anieli

.github/workflows/ci.yml

@@ -40,12 +40,6 @@ jobs:
     strategy:
       matrix:
         include:
-          - python: '3.6'
-            toxenv: py36
-          - python: '3.7'
-            toxenv: py37
-          - python: '3.8'
-            toxenv: py38
           - python: '3.9'
             toxenv: py39
           - python: '3.10'
@@ -54,6 +48,8 @@ jobs:
             toxenv: py311
           - python: '3.12'
             toxenv: py312
+          - python: '3.13'
+            toxenv: py313
           - python: pypy3.9
             toxenv: pypy3
     steps: