Standardize styling for hr elements and remove custom hr styling and classes that were no longer needed.

Fix styling on a few hr elements that looked wrong after global style was applied

styles/sections/_application_edit.scss

@@ -77,11 +77,6 @@
       }
     }
   }
-
-  hr {
-    border: none;
-    border-bottom: 1px solid $color-gray-lighter;
-  }
 }
 
 .environment-roles {

styles/sections/_home.scss

@@ -18,13 +18,6 @@
     margin-top: 0;
   }
 
-  hr {
-    border: 0;
-    border-bottom: 1px solid $color-gray-light;
-    margin-top: $gap * 4;
-    margin-bottom: $gap * 4;
-  }
-
   .links {
     justify-content: flex-start;
 

styles/sections/_reports.scss

@@ -8,7 +8,6 @@
   &__col {
     hr {
       margin: (2 * $gap) 0;
-      border-bottom: 1px solid $color-gray-lightest;
     }
 
     @include media($medium-screen) {

styles/sections/_task_order.scss

@@ -29,10 +29,8 @@
   }
 
   hr {
-    border: 0;
-    margin-top: $gap * 4;
-    margin-bottom: $gap * 4;
-    border-bottom: 1px solid $color-gray-lighter;
+    margin-left: auto;
+    margin-right: auto;
   }
 
   table {