Set tint to @null for gear icon.

This still works for dark mode, because the color used in the
ic_settings_gear_24dp.xml file is adapative
(@color/default_icon_color_secondary).


Bug: b/166795933
Change-Id: Ia229e019701511ae39642eac4c28525d986212f7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2406720Reviewed-by: David Trainor <dtrainor@chromium.org>
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Commit-Queue: Jonathan Freed <freedjm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807104}

chrome/android/java/res/layout/new_tab_page_feed_v2_expandable_header.xml

@@ -40,5 +40,5 @@
         android:src="@drawable/ic_settings_gear_24dp"
         android:contentDescription="@string/accessibility_ntp_feed_menu_button"
         app:menuMaxWidth="@dimen/feed_header_menu_max_width"
-        app:tint="@color/default_icon_color_tint_list" />
+        app:tint="@null" />
 </org.chromium.chrome.browser.ntp.snippets.SectionHeaderView>

chrome/android/java/res/layout/new_tab_page_snippets_expandable_header_with_menu.xml

@@ -37,5 +37,5 @@
         android:src="@drawable/ic_settings_gear_24dp"
         android:contentDescription="@string/accessibility_ntp_feed_menu_button"
         app:menuMaxWidth="@dimen/feed_header_menu_max_width"
-        app:tint="@color/default_icon_color_tint_list" />
+        app:tint="@null" />
 </org.chromium.chrome.browser.ntp.snippets.SectionHeaderView>