[Autofill Assistant] Make trigger condition element checks non-strict.

This brings them in line with regular script preconditions.

Bug: b/175785117
Change-Id: I3fbc991b6c7a97c6b8134b989795cc4e96c44311
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611718
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Commit-Queue: Jordan Demeulenaere <jdemeulenaere@chromium.org>
Auto-Submit: Clemens Arbesser <arbesser@google.com>
Reviewed-by: Jordan Demeulenaere <jdemeulenaere@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840621}

components/autofill_assistant/browser/trigger_scripts/dynamic_trigger_conditions.cc

@@ -91,7 +91,7 @@ void DynamicTriggerConditions::Update(WebController* web_controller,
   callback_ = std::move(callback);
   for (const auto& selector : selectors_) {
     web_controller->FindElement(
-        selector, /* strict = */ true,
+        selector, /* strict = */ false,
         base::BindOnce(&DynamicTriggerConditions::OnFindElement,
                        weak_ptr_factory_.GetWeakPtr(), selector));
   }