Pin the MCP conformance tester package #1714

Job	Run time
build (ubuntu-latest, Release)	10m 57s
build (macos-latest, Debug)	9m 27s
build (ubuntu-latest, Debug)	5m 30s
build (windows-latest, Debug)	9m 10s
build (windows-latest, Release)	9m 42s
build (macos-latest, Release)	8m 4s
publish-coverage	0s
build (ubuntu-latest, Debug)	11m 31s
build (windows-latest, Release)	13m 18s
build (ubuntu-latest, Release)	5m 24s
build (windows-latest, Debug)	9m 8s
build (macos-latest, Release)	8m 4s
build (macos-latest, Debug)	9m 27s
publish-coverage	-1s
	1h 49m 41s

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