ci: run JSON-RPC tests with Python 3.13

Author: link2xt

.github/workflows/ci.yml

@@ -281,11 +281,11 @@ jobs:
       matrix:
         include:
           - os: ubuntu-latest
-            python: 3.14
+            python: 3.13
           - os: macos-latest
-            python: 3.14
+            python: 3.13
           - os: windows-latest
-            python: 3.14
+            python: 3.13
 
           # PyPy tests
           - os: ubuntu-latest