[FLINK-38289] Remove python 3.8 testing as support was dropped in Flink 2.1

Signed-off-by: Thomas Cooper <[email protected]>

Author: tomncooper

flink-python/tox.ini

@@ -21,7 +21,7 @@
 # in multiple virtualenvs. This configuration file will run the
 # test suite on all supported python versions.
 # new environments will be excluded by default unless explicitly added to envlist.
-envlist = {py38, py39, py310}-cython
+envlist = {py39, py310, py311}-cython
 
 [testenv]
 whitelist_externals = /bin/bash