chore(NODE-5585): use mongodb-legacy 6 for tests (#3849)

Author: nbbeeken

package-lock.json

@@ -97,7 +97,7 @@
     "mocha": "^10.2.0",
     "mocha-sinon": "^2.1.2",
     "mongodb-client-encryption": "^6.0.0",
-    "mongodb-legacy": "github:mongodb-js/nodejs-mongodb-legacy#main",
+    "mongodb-legacy": "^6.0.0",
     "nyc": "^15.1.0",
     "prettier": "^2.8.8",
     "semver": "^7.5.0",