ci: Use 3.15-dev

Author: pawamoy

.github/workflows/ci.yml

@@ -44,7 +44,7 @@ jobs:
         - os: ubuntu-latest
           python-version: "3.13"
         - os: ubuntu-latest
-          python-version: "3.15"
+          python-version: "3.15-dev"
 
     runs-on: ${{ matrix.os }}
 
@@ -104,7 +104,7 @@ jobs:
         - "3.12"
         - "3.13"
         - "3.14"
-        - "3.15"
+        - "3.15-dev"
         resolution:
         - highest
         - lowest-direct