Stop making appearance:base-select submit form on enter

When customizable select was going to be a new element, we decided on
the enter form submission behavior here:
openui/open-ui#386

It got negative feedback in the attached bug since customizable select
now reuses the select element, so this patch reverts the behavior and
makes it do the same thing as appearance:auto select.

Fixed: 429647164
Change-Id: Ia40a309270d8f34123c5f697f583ae982eebd24d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6959790
Commit-Queue: Joey Arhar <[email protected]>
Reviewed-by: Mason Freed <[email protected]>
Cr-Commit-Position: refs/heads/main@{#1520122}

Author: josepharhar

html/semantics/forms/the-select-element/customizable-select/select-keyboard-behavior.optional.html

@@ -140,7 +140,7 @@
     }, {once: true});
     await test_driver.send_keys(select, Enter);
     await new Promise(requestAnimationFrame);
-    assert_true(formWasSubmitted,
+    assert_false(formWasSubmitted,
       'Enter should submit the form when the listbox is closed.');
     assert_false(select.matches(':open'),
       'Enter should not open the listbox when it is in a form.');