Remove obsolete styles

These styles aren't necessary since commit aabf8493f. Now the "Go back"
link in the budgets section can use the same color as in the other
sections, while the other texts inherit the usual colors.

app/assets/stylesheets/participation.scss

@@ -1235,16 +1235,6 @@
     margin-bottom: 0;
   }
 
-  h1,
-  h2,
-  h3,
-  .back,
-  .icon-angle-left,
-  p,
-  a {
-    color: $text;
-  }
-
   .tagline {
     display: block;
     font-size: $small-font-size;