MNT: Drop 3.9 from tested Python version matrix

Drop 3.9 from tested Python version matrix.

Co-authored-by: Oscar Esteban <[email protected]>

Author: jhlegarreta

.github/workflows/tox.yml

@@ -118,17 +118,17 @@ jobs:
     needs: [cache-test-data]
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
         dependencies: [latest, pre]
         include:
-          - python-version: "3.9"
+          - python-version: "3.10"
             dependencies: min
         exclude:
           # Do not test pre-releases for versions out of SPEC0
-          - python-version: "3.9"
-            dependencies: pre
           - python-version: "3.10"
             dependencies: pre
+          - python-version: "3.11"
+            dependencies: pre
 
     env:
       DEPENDS: ${{ matrix.dependencies }}