chore: remove mysql57 #700

Job	Run time
run_ci (ubuntu-20.04, 3.11, discovery+lms+forum)	7m 37s
run_ci (ubuntu-20.04, 3.11, discovery+lms+forum)	7m 37s
run_ci (ubuntu-20.04, 3.11, registrar+lms)	7m 16s
run_ci (ubuntu-20.04, 3.11, registrar+lms)	7m 16s
run_ci (ubuntu-20.04, 3.11, ecommerce+lms)	7m 21s
run_ci (ubuntu-20.04, 3.11, ecommerce+lms)	7m 21s
run_ci (ubuntu-20.04, 3.11, edx_notes_api+lms)	7m 19s
run_ci (ubuntu-20.04, 3.11, edx_notes_api+lms)	7m 19s
run_ci (ubuntu-20.04, 3.11, credentials+lms)	7m 43s
run_ci (ubuntu-20.04, 3.11, credentials+lms)	7m 43s
run_ci (ubuntu-20.04, 3.11, xqueue)	2m 51s
run_ci (ubuntu-20.04, 3.11, xqueue)	2m 51s
run_ci (ubuntu-20.04, 3.11, analyticsapi+insights+lms)	7m 38s
run_ci (ubuntu-20.04, 3.11, analyticsapi+insights+lms)	7m 8s
run_ci (ubuntu-20.04, 3.11, designer+lms)	7m 11s
run_ci (ubuntu-20.04, 3.11, designer+lms)	7m 11s
run_ci (ubuntu-20.04, 3.11, enterprise-subsidy+enterprise-catalog+enterprise-access+lms)	7m 47s
run_ci (ubuntu-20.04, 3.11, enterprise-subsidy+enterprise-catalog+enterprise-access+lms)	7m 47s
run_ci (ubuntu-20.04, 3.11, license-manager+lms)	6m 59s
run_ci (ubuntu-20.04, 3.11, license-manager+lms)	6m 59s
	2h 18m 54s

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