Update Yarn to v1.9.4 (#3881)
Update Yarn to v1.9.4 (#3881)


edmorley/treeherder,edmorley/treeherder,KWierso/treeherder,edmorley/treeherder,KWierso/treeherder,edmorley/treeherder,KWierso/treeherder,KWierso/treeherder