Remove obsolete CSS selectors

The `investment-project` and `investment-project-show` classes aren't
used since commit d0b8fef6b.

app/assets/stylesheets/participation.scss

@@ -329,7 +329,6 @@
 .debate-show,
 .proposal-show,
 .poll-question-show,
-.investment-project-show,
 .budget-investment-show,
 .polls-show,
 .debate-quiz,
@@ -491,13 +490,11 @@
   color: $text;
 }
 
-.investment-project-show p,
 .budget-investment-show p {
   word-break: break-word;
 }
 
 .proposal-show,
-.investment-project-show,
 .budget-investment-show {
 
   .supports {
@@ -644,7 +641,6 @@
 
 .debate,
 .proposal,
-.investment-project,
 .budget-investment,
 .legislation,
 .communities-show {
@@ -799,8 +795,6 @@
   }
 }
 
-.investment-project,
-.investment-project-show,
 .budget-investment,
 .budget-investment-show {
 
@@ -858,7 +852,6 @@
   }
 }
 
-.investment-project-show .supports,
 .budget-investment-show .supports {
   border: 0;
 }
@@ -870,8 +863,6 @@
   }
 }
 
-.investment-project .no-button,
-.investment-project-show .no-button,
 .budget-investment .no-button,
 .budget-investment-show .no-button {
   display: block;