Raise mypy version to 1.15

Author: oxan

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.11
+          python-version: 3.13
       - name: Install dependencies
         run: pip install '.[dev]'
       - name: Run mypy

pyproject.toml

@@ -46,7 +46,7 @@ dependencies = [
 dev = [
     "django-stubs",
     "djangorestframework-stubs",
-    "mypy ~= 1.8.0",
+    "mypy ~= 1.15.0",
 ]
 test = [
     "coverage[toml]",