Remove unnecessary background color definitions

These elements already inherit these background colors form their parent
elements. Defining them explicitly makes it harder to change them and it
also makes it harder to customize the styles in other CONSUL
installations.

app/assets/stylesheets/admin.scss

@@ -509,10 +509,6 @@ code {
 // 04. Stats
 // ---------
 
-.stats {
-  background: #fff;
-}
-
 .stats-numbers {
   p {
     color: $text-medium;

app/assets/stylesheets/layout.scss

@@ -345,7 +345,6 @@ a {
       font-weight: bold;
 
       &::after {
-        background: $brand;
         border-bottom: 2px solid;
         bottom: 0;
         content: "";
@@ -1834,7 +1833,6 @@ table {
   }
 
   .reply {
-    background: #fff;
     border: 1px solid $border;
     border-left: 0;
     border-right: 0;
@@ -2177,7 +2175,6 @@ table {
   .debates-inner,
   .proposals-inner,
   .budget-investments-inner {
-    background: #fff;
     max-height: rem-calc(350);
 
     @include breakpoint(small) {

app/assets/stylesheets/legislation.scss

@@ -40,7 +40,6 @@
 // -----------------
 .legislation {
   margin: 0 0 $line-height;
-  background: #fff;
   border: 1px solid;
   border-color: #e5e6e9 #dfe0e4 #d0d1d5;
   border-radius: 0;

app/assets/stylesheets/legislation_process.scss

@@ -583,7 +583,6 @@
     }
 
     .calc-comments {
-      background: #fff;
       cursor: auto;
 
       @include breakpoint(small only) {