feat!: remove `skill_levels` API #31595

Job	Run time
collect-and-verify	4m 32s
lms-1(py=3.11,dj=pinned,mongo=7.0)	10m 19s
lms-2(py=3.11,dj=pinned,mongo=7.0)	12m 11s
lms-3(py=3.11,dj=pinned,mongo=7.0)	14m 56s
lms-4(py=3.11,dj=pinned,mongo=7.0)	19m 36s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 39s
lms-6(py=3.11,dj=pinned,mongo=7.0)	16m 11s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	11m 42s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	14m 55s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 33s
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 42s
cms-2(py=3.11,dj=pinned,mongo=7.0)	14m 37s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 25s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 40s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 55s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 54s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 45s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 58s
compile-warnings-report	13s
coverage (3.11)	1m 46s
Unit tests successful	3s
merge-artifacts	6s
	3h 24m 12s

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