[CrOS Settings] Fix padding for 'Set Up' Messages button.

Currently, the 'Set up' Messages button has no margin-inline-end.  It's
corresponding toggle button does, however, have a margin
(see "After screenshot" of
https://chromium-review.googlesource.com/c/chromium/src/+/1879445).

This is because CL 1879445 removes padding when the .no-padding class is
applied, which is the case for the settings-box ancestor of the button,
a feature-controller slot. As a result, bookend children of settings-box
must account for the padding loss via a .margin-matches-padding class.
CL 1879445 should have applied margin-matches-padding class around the
slot instead of only applying the .margin-matches-padding class to the
toggle contained within the slot.

Before screenshot--
https://screenshot.googleplex.com/WDtZVWyZDbB

After screenshot--

https: //screenshot.googleplex.com/ZgLoy8DPEYq
Bug: 1008361
Change-Id: I6583795757f4bf3685132a2543481e777f64a898
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1910873
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Reviewed-by: Dan Beam <dbeam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714682}

chrome/browser/resources/settings/multidevice_page/multidevice_feature_item.html

@@ -63,17 +63,18 @@
           restamp>
         <cr-policy-indicator indicator-type="userPolicy"></cr-policy-indicator>
       </template>
+      <div class="margin-matches-padding">
         <slot name="feature-controller">
           <!-- This settings-multidevice-feature-toggle is the default controller.
           If an element with slot="feature-controller" is attached, it will
           replace this one. -->
           <settings-multidevice-feature-toggle
-            class="margin-matches-padding"
               feature="[[feature]]"
               page-content-data="[[pageContentData]]">
           </settings-multidevice-feature-toggle>
         </slot>
       </div>
+    </div>
   </template>
   <script src="multidevice_feature_item.js"></script>
 </dom-module>