[Autofill Assistant] Add missing file comment

Bug: none
Change-Id: I3e17122036375f5738afdeeee7944bb12b2648c1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2484599
Auto-Submit: Sandro Maggi <sandromaggi@google.com>
Reviewed-by: Luca Hunkeler <hluca@google.com>
Commit-Queue: Luca Hunkeler <hluca@google.com>
Cr-Commit-Position: refs/heads/master@{#818443}

chrome/android/features/autofill_assistant/javatests/src/org/chromium/chrome/browser/autofill_assistant/AutofillAssistantInputActionIntegrationTest.java

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
 package org.chromium.chrome.browser.autofill_assistant;
 
 import static androidx.test.espresso.Espresso.onView;