fix: option is optional

Author: durran

src/index.ts

@@ -68,7 +68,7 @@ type MongoCryptConstructorOptions = {
   cryptSharedLibPath?: string;
   bypassQueryAnalysis?: boolean;
   /** Configure the time to expire the DEK from the cache. */
-  keyExpirationMS: number;
+  keyExpirationMS?: number;
   /** TODO(NODE-6793): remove this option and have it always set in the next major */
   enableMultipleCollinfo?: boolean;
 };