refactor!: remove md4 and related ENABLE_BLAKE2B_HASHING feature flag #32765

Job	Run time
collect-and-verify	4m 30s
lms-1(py=3.11,dj=pinned,mongo=7.0)	9m 58s
lms-2(py=3.11,dj=pinned,mongo=7.0)	11m 36s
lms-3(py=3.11,dj=pinned,mongo=7.0)	15m 40s
lms-4(py=3.11,dj=pinned,mongo=7.0)	22m 40s
lms-5(py=3.11,dj=pinned,mongo=7.0)	11m 31s
lms-6(py=3.11,dj=pinned,mongo=7.0)	15m 58s
openedx-1-with-lms(py=3.11,dj=pinned,mongo=7.0)	10m 52s
openedx-2-with-lms(py=3.11,dj=pinned,mongo=7.0)	14m 20s
openedx-1-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 25s
openedx-2-with-cms(py=3.11,dj=pinned,mongo=7.0)	7m 59s
cms-1(py=3.11,dj=pinned,mongo=7.0)	4m 37s
cms-2(py=3.11,dj=pinned,mongo=7.0)	12m 51s
common-with-lms(py=3.11,dj=pinned,mongo=7.0)	9m 18s
common-with-cms(py=3.11,dj=pinned,mongo=7.0)	5m 14s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 21s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 21s
xmodule-with-cms(py=3.11,dj=pinned,mongo=7.0)	8m 32s
xmodule-with-lms(py=3.11,dj=pinned,mongo=7.0)	8m 56s
Unit tests successful	2s
compile-warnings-report	8s
coverage (3.11)	1m 44s
merge-artifacts	6s
	3h 21m 39s

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