pixi: Use python 3.10 as oldest python version and 3.14 as latest

Author: jorisv

.github/workflows/macos-linux-windows-pixi.yml

@@ -39,7 +39,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest, macos-15-intel]
-        environment: [all, all-py39]
+        environment: [all, all-python-oldest]
         build_type: [Release, Debug]
         cxx_options: ['', '-mavx2']