Fix alignment of report-a-problem at certain widths

At a breakpoint below 1020 the report a problem link, and
form, weren't aligned to the grid of the rest of the page, and were
indented by an additional 30px on each side.

This was caused by `%site-width-container` being used on the report
a problem containers, within `#wrapper`, which already extends
`%site-width-container`, causing double margins.

As the report a problem elements already inside a page width container
it's same to remove the use of `%site-width-container` for them.

app/assets/stylesheets/helpers/_report-a-problem.scss

@@ -3,7 +3,6 @@
 }
 
 .report-a-problem-container{
-  @extend %site-width-container;
   clear: both;
 
   .report-a-problem-inner {
@@ -82,6 +81,5 @@
 }
 
 .report-a-problem-toggle-wrapper {
-  @extend %site-width-container;
   clear:both;
 }