Bump Microsoft.EntityFrameworkCore.Abstractions from 6.0.15 to 6.0.20 #1106

Job	Run time
calc-version	22s
CodeQL-Analyze	10m 28s
analyze	8m 9s
integration-test (AcrApi, ef)	3m 55s
integration-test (AcrApi, mongodb)	3m 8s
integration-test (DicomDimseScp, ef)	6m 18s
integration-test (DicomDimseScp, mongodb)	4m 22s
integration-test (DicomDimseScu, ef)	3m 5s
integration-test (DicomDimseScu, mongodb)	3m 2s
integration-test (DicomWebExport, ef)	3m 2s
integration-test (DicomWebExport, mongodb)	3m 7s
integration-test (DicomWebStow, ef)	4m 32s
integration-test (DicomWebStow, mongodb)	4m 36s
integration-test (HealthLevel7, ef)	5m 9s
integration-test (HealthLevel7, mongodb)	5m 12s
integration-test (Fhir, ef)	3m 20s
integration-test (Fhir, mongodb)	3m 38s
unit-test	7m 31s
docs	5m 7s
build (ubuntu-latest)	4m 12s
build (windows-latest)	6m 8s
release	0s
	1h 38m 23s

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