Fix py314 basepython configuration to use python3

Change basepython from 'python' to 'python3' to avoid tox error:
"env name py314 conflicting with base python python"

Using 'python3' is specific enough for tox while still working with
both regular Python 3.14 and free-threading Python 3.14t builds in
GitHub Actions.

Author: theskumar

tox.ini

@@ -24,7 +24,7 @@ depends =
     coverage-report: py{310,311,312,313,314},pypy3
 
 [testenv:py314]
-basepython = python
+basepython = python3
 
 [testenv:lint]
 skip_install = true