[Autofill Assistant] Use android:color/transparent instead of autofill_assistant_transparent

Change-Id: Ife5804b2897aac9463d91a5e20e154678ce274bd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1841633
Auto-Submit: Jordan Demeulenaere <jdemeulenaere@chromium.org>
Reviewed-by: Clemens Arbesser <arbesser@google.com>
Commit-Queue: Clemens Arbesser <arbesser@google.com>
Cr-Commit-Position: refs/heads/master@{#702889}

chrome/android/features/autofill_assistant/java/res/drawable/autofill_assistant_actions_gradient.xml

@@ -3,5 +3,5 @@
     <gradient
         android:angle="0"
         android:startColor="@color/sheet_bg_color"
-        android:endColor="@color/autofill_assistant_transparent"/>
+        android:endColor="@android:color/transparent"/>
 </shape>
\ No newline at end of file

chrome/android/features/autofill_assistant/java/res/values-v17/colors.xml

@@ -11,6 +11,5 @@
     -->
     <color name="autofill_assistant_light_grey">@color/modern_grey_300</color>
     <color name="autofill_assistant_light_blue">#E9F0FD</color>
-    <color name="autofill_assistant_transparent">#00FFFFFF</color>
     <color name="autofill_assistant_actions_shadow_color">#40CCCCCC</color>
 </resources>