chore: fix typo

- for some reason this edk2 entry was missing PYTHON_VERSION argument
- this is only cosmetic change, it does not change any contianer as
  Python3 is already default, it just makes it more explicit

Signed-off-by: AtomicFS <vojtech.vesely@9elements.com>

Author: AtomicFS

docker/compose.yaml

@@ -150,6 +150,7 @@ services:
         - INTERMEDIATE_IMAGE=universalpayload
         - GCC_VERSION=9
         - PYTHON_PACKAGES=python-is-python3 python2 python3
+        - PYTHON_VERSION=python3
         - NODESOURCE=https://deb.nodesource.com/setup_20.x
   edk2-stable202302:
     build: