fix(clerk-js): Call openSignIn instead of openSignUp (#4764)

Author: dstaley

.changeset/fresh-turtles-bow.md

@@ -0,0 +1,2 @@
+---
+---

packages/clerk-js/sandbox/app.ts

@@ -102,7 +102,7 @@ function mountOpenSignInButton(element: HTMLDivElement, props) {
   const button = document.createElement('button');
   button.textContent = 'Open Sign In';
   button.onclick = () => {
-    Clerk?.openSignUp(props);
+    Clerk?.openSignIn(props);
   };
   element.appendChild(button);
 }