fix date in test (#937)

* fix date in test

Co-authored-by: Mike Bostock <[email protected]>

Author: Fil

test/plots/yearly-requests-dot.js

@@ -3,9 +3,9 @@ import * as Plot from "@observablehq/plot";
 
 export default async function() {
   const requests = [
-    [new Date("2002-1-01"), 9],
-    [new Date("2003-1-01"), 17],
-    [new Date("2005-1-01"), 5]
+    [new Date("2002-01-01"), 9],
+    [new Date("2003-01-01"), 17],
+    [new Date("2005-01-01"), 5]
   ];
   return Plot.plot({
     label: null,