Bump mongodb-memory-server from 8.14.0 to 8.15.1 #225

Job	Run time
Library Validation (ubuntu-latest, 16.x)	1m 4s
Library Validation (ubuntu-latest, 16.x)	1m 4s
Library Validation (ubuntu-latest, 18.x)	46s
Library Validation (ubuntu-latest, 18.x)	46s
Library Validation (ubuntu-latest, 20.x)	51s
Library Validation (ubuntu-latest, 20.x)	51s
Library Validation (windows-latest, 16.x)	6h 0m 1s
Library Validation (windows-latest, 16.x)	1m 43s
Library Validation (windows-latest, 18.x)	2m 54s
Library Validation (windows-latest, 18.x)	2m 54s
Library Validation (windows-latest, 20.x)	2m 31s
Library Validation (windows-latest, 20.x)	2m 31s
NestJS Example App Validation (ubuntu-latest, 16.x)	1m 31s
NestJS Example App Validation (ubuntu-latest, 16.x)	1m 31s
NestJS Example App Validation (ubuntu-latest, 20.x)	1m 22s
NestJS Example App Validation (ubuntu-latest, 20.x)	1m 22s
NestJS Example App Validation (windows-latest, 16.x)	6m 55s
NestJS Example App Validation (windows-latest, 16.x)	6m 55s
NestJS Example App Validation (windows-latest, 20.x)	2m 0s
NestJS Example App Validation (windows-latest, 20.x)	2m 0s
	6h 41m 32s

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