improves css units

app/assets/stylesheets/participation.scss

@@ -507,11 +507,11 @@
   li::before {
     content: '';
     position: absolute;
-    top: rem-calc(5);
+    top: 5px;
     transform: translateX(-50%);
     width: rem-calc(20);
     height: rem-calc(20);
-    border-radius: 50%;
+    border-radius: rem-calc(20);
     background: $budget;
     z-index: 2;
   }
@@ -523,23 +523,22 @@
     bottom: 100%;
     height: 100%;
     position: absolute;
-    top: rem-calc(25);
+    top: 25px;
     z-index: 1;
   }
 }
 
 .tab-milestones ul .milestone-content {
   position: relative;
-  padding: rem-calc(3) rem-calc(10);
+  padding: $line-height / 6 $line-height / 2;
 
   h3 {
-    font-size: 1.2rem;
     margin-bottom: 0;
   }
 
   .milestone-date {
     color: $text-medium;
-    font-size: 0.9rem;
+    font-size: $small-font-size;
   }
 }
 
@@ -576,7 +575,7 @@
 .tab-milestones .timeline ul li:nth-child(even) {
 
   .milestone-content {
-    left: rem-calc(15);
+    left: 15px;
   }
 }
 
@@ -591,7 +590,7 @@
 
         .milestone-content {
           text-align: left;
-          left: rem-calc(15);
+          left: 15px;
         }
       }
     }