chore: remove macos-13 from CI

(it's slow and going to be EOL in November 2025 anyway)

.github/workflows/ci.yml

@@ -159,11 +159,8 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ "macos-13", "macos-14", "macos-15" ]
+        os: [ "macos-14", "macos-15" ]
         python-version: ["3.10", "3.11", "3.12", "3.13"]
-        exclude:
-        - os: macos-13
-          python-version: "3.13"
 
     steps:
     - uses: actions/checkout@v4