Change flake8 pipeline's python image

Currently, the flake8 pipeline uses python3.8 image. This old image limits the supported versions of PySide6, so we need to update the image to a more recent one so that we can request more recent PySide6 versions.

conda.recipe/meta.yaml

@@ -20,7 +20,7 @@ requirements:
     - python >=3.9
     - numpy >=1.23.0,<2.0
     - obspy >=1.3.0
-    - PySide6>=6.7
+    - PySide6>=6.5.2
     - matplotlib>=3.6.2
 
 test: