remove 3.9 tests

Author: choldgraf

.github/workflows/tests.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest]
-        python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
+        python-version: ["3.10", "3.11", "3.12", "3.13"]
         sphinx: [""]  # Newest Sphinx (any)
         myst-parser: [""]  # Newest MyST Parser (any)
         include:
@@ -41,7 +41,7 @@ jobs:
             pillow: "==11.0.0"
           # Oldest known-compatible dependencies
           - os: ubuntu-latest
-            python-version: "3.9"
+            python-version: "3.10"
             sphinx: "==5.0.0"
             myst-parser: "==1.0.0"
             pillow: "==11.0.0"