Remove unnecessary HTML classes

There are negative margins on .expanded.budget elements, and so these
rules are redundant.

app/views/budgets/ballot/_ballot.html.erb

@@ -1,4 +1,4 @@
-<div class="budget-header no-margin-top padding">
+<div class="budget-header padding">
   <div class="row">
     <%= back_link_to @ballot_referer %>
 

app/views/budgets/groups/show.html.erb

@@ -2,7 +2,7 @@
   <%= render "shared/canonical", href: budget_group_url(filter: @current_filter) %>
 <% end %>
 
-<div class="budget-header no-margin-top">
+<div class="budget-header">
   <div class="row">
     <div class="small-12 medium-9 column padding">
       <%= back_link_to budgets_path %>

app/views/budgets/index.html.erb

@@ -121,7 +121,7 @@
     <% end %>
   </div>
 <% else %>
-  <div class="budget-header no-margin-top margin-bottom">
+  <div class="budget-header margin-bottom">
     <div class="row">
       <div class="small-12 medium-9 column padding">
           <h1><%= t("budgets.index.title") %></h1>

app/views/budgets/show.html.erb

@@ -2,7 +2,7 @@
   <%= render "shared/canonical", href: budget_url(@budget, filter: @current_filter) %>
 <% end %>
 
-<div class="budget-header no-margin-top">
+<div class="budget-header">
   <div class="row" data-equalizer data-equalizer-on="medium">
     <div class="small-12 medium-9 column padding" data-equalizer-watch>
       <%= back_link_to budgets_path %>