Bump CPython to 3.14rc3 (#798)

Author: zanieb

pythonbuild/downloads.py

@@ -93,10 +93,10 @@
         "python_tag": "cp313",
     },
     "cpython-3.14": {
-        "url": "https://www.python.org/ftp/python/3.14.0/Python-3.14.0rc2.tar.xz",
-        "size": 23566140,
-        "sha256": "bc62854cf232345bd22c9091a68464e01e056c6473a3fffa84572c8a342da656",
-        "version": "3.14.0rc2",
+        "url": "https://www.python.org/ftp/python/3.14.0/Python-3.14.0rc3.tar.xz",
+        "size": 23585028,
+        "sha256": "646dc945e49c73a141896deda12d43f3f293fd69426774c16fc43496180e8fcd",
+        "version": "3.14.0rc3",
         "licenses": ["Python-2.0", "CNRI-Python"],
         "license_file": "LICENSE.cpython.txt",
         "python_tag": "cp314",