Update tox.ini to remove Python 3.8 support #30154

Job	Run time
collect-and-verify	4m 39s
lms-1(py=3.11,dj=pinned,mongo=7.0)	18s
lms-2(py=3.11,dj=pinned,mongo=7.0)	22s
lms-3(py=3.11,dj=pinned,mongo=7.0)	20s
lms-4(py=3.11,dj=pinned,mongo=7.0)	29s
lms-5(py=3.11,dj=pinned,mongo=7.0)	18s
lms-6(py=3.11,dj=pinned,mongo=7.0)	18s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	20s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	26s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	21s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	21s
cms-1(py=3.11,dj=pinned,mongo=7.0)	24s
cms-2(py=3.11,dj=pinned,mongo=7.0)	18s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	19s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	28s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	18s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	17s
Unit tests successful	4s
compile-warnings-report	0s
coverage	0s
merge-artifacts	0s
	10m 20s

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