Changing Member.premium_since back from Date to number fixes an error in the Discord electron client related to rendering premium status. (#669)

Client throws "Invalid time value", so I'm guessing it's something to do with premium_since not being the date format they want ( allegedly ISO8601, but works with a plain number, so wtf )

util/src/entities/Member.ts

@@ -86,7 +86,7 @@ export class Member extends BaseClassWithoutId {
 	joined_at: Date;
 
 	@Column({ nullable: true })
-	premium_since?: Date;
+	premium_since?: number;
 
 	@Column()
 	deaf: boolean;