LibWeb/Tests: Better trigger for table style update test

Author: https://github.com/axgallo
Commit: https://github.com/SerenityOS/serenity/commit/fc45831fb3
Pull-request: https://github.com/SerenityOS/serenity/pull/19585

Tests/LibWeb/Layout/expected/table/propagate-style-update-to-wrapper.txt

@@ -14,5 +14,3 @@ Viewport <#document> at (0,0) content-size 800x600 children: not-inline
                 TextNode <#text>
             BlockContainer <(anonymous)> (not painted) children: inline
               TextNode <#text>
-      BlockContainer <(anonymous)> at (8,8) content-size 784x0 children: inline
-        TextNode <#text>

Tests/LibWeb/Layout/input/table/propagate-style-update-to-wrapper.html

@@ -1,12 +1,13 @@
+<script>
+    document.addEventListener("DOMContentLoaded", function () {
+        let t = document.querySelector("#t");
+        t.style.position = "absolute";
+        window.getComputedStyle(t).position;
+    }, false);
+</script>
+
 <table id="t">
     <tr>
         <td></td>
     </tr>
-</table>
-
-<script>
-    t = document.querySelector("#t");
-    console.log(t);
-    t.style.position = "absolute";
-    window.getComputedStyle(t);
-</script>
+</table>