feat!: remove `skill_levels` API (#35863) #31606

Job	Run time
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 34s
collect-and-verify	4m 21s
lms-2(py=3.11,dj=pinned,mongo=7.0)	11m 55s
lms-3(py=3.11,dj=pinned,mongo=7.0)	15m 19s
lms-4(py=3.11,dj=pinned,mongo=7.0)	20m 10s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 5s
lms-6(py=3.11,dj=pinned,mongo=7.0)	15m 42s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 55s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	14m 28s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 51s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	6m 34s
cms-1(py=3.11,dj=pinned,mongo=7.0)	5m 16s
cms-2(py=3.11,dj=pinned,mongo=7.0)	12m 52s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 55s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 56s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 48s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 45s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	9m 23s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 33s
compile-warnings-report	9s
Unit tests successful	4s
coverage (3.11)	1m 47s
merge-artifacts	7s
	3h 22m 29s

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