MDL-72790 block_timeline: Set content width consistent with other blocks

Previously the margins were set with the container class, which meant
the content was narrower than other blocks. This does not need to be
managed by the block since the dashboard will soon manage this with
its own max width.

blocks/timeline/templates/main.mustache

@@ -24,7 +24,7 @@
 }}
 
 <div id="block-timeline-{{uniqid}}" class="block-timeline" data-region="timeline">
-    <div class="container p-0 px-2">
+    <div class="p-0 px-2">
         <div class="row no-gutters">
             <div class="mr-2 mb-1">
                 {{> block_timeline/nav-day-filter }}
@@ -38,7 +38,7 @@
         </div>
         <div class="pb-3 px-2 border-bottom"></div>
     </div>
-    <div class="container p-0">
+    <div class="p-0">
         {{> block_timeline/view }}
     </div>
 </div>