Clean up forum nav Sass

Now that the sidebar class is no longer used, many rules no longer need
!important and can move out of _shame.scss.

lms/static/sass/discussion/elements/_navigation.scss

@@ -2,6 +2,7 @@
   @include box-sizing(border-box);
   float: left;
   position: relative;
+  width: 31%;
   border: 1px solid #aaa;
   border-radius: 3px;
 }
@@ -95,11 +96,18 @@
 }
 
 .forum-nav-browse-submenu {
+  padding-left: $baseline;
   list-style: none;
 }
 
 .forum-nav-browse-title {
   display: block;
+  border-bottom: 1px solid $gray-l3;
+  padding: ($baseline/2) ($baseline/2);
+
+  &:hover, &:focus {
+    background: $forum-color-active-thread;
+  }
 }
 
 .forum-nav-browse-title .icon {
@@ -147,10 +155,20 @@
 
 .forum-nav-thread {
   border-bottom: 1px solid $gray-l3;
+  background-color: $gray-l5;
+
+  &.is-unread {
+    background-color: $white;
+  }
 }
 
 .forum-nav-thread-link {
   display: block;
+  padding: ($baseline/4) ($baseline/2);
+
+  &.is-active, &:hover, &:focus {
+    background-color: $forum-color-active-thread;
+  }
 }
 
 %forum-nav-thread-wrapper {
@@ -178,8 +196,10 @@
   @extend %t-weight4;
   @include font-size(9);
   display: inline;
+  margin-top: ($baseline/4);
   border: 1px solid;
   border-radius: 3px;
+  padding: 1px 6px;
   text-transform: uppercase;
   white-space: nowrap;
 
@@ -281,14 +301,25 @@
   }
 }
 
+.forum-nav-load-more {
+  border-bottom: 1px solid $gray-l3;
+  background-color: $gray-l5;
+}
+
 %forum-nav-load-more-content {
   display: block;
+  padding: $baseline 0;
   text-align: center;
 }
 
 .forum-nav-load-more-link {
   @extend %forum-nav-load-more-content;
   color: $link-color;
+
+  &:hover, &:focus {
+    color: $link-color;
+    background-color: $forum-color-active-thread;
+  }
 }
 
 .forum-nav-loading {

lms/static/sass/discussion/utilities/_shame.scss

@@ -29,15 +29,6 @@
   position: relative;
 }
 
-// The sidebar class does a lot of things that we don't want in the thread list;
-// the following rules contain styling that is necessary and would otherwise
-// reside in elements/_navigation.scss if the sidebar styling did not make the
-// !important directive necessary.
-
-.forum-nav {
-  width: 31% !important;
-}
-
 // ------------------------
 // navigation - browse menu
 // ------------------------
@@ -65,25 +56,10 @@
 // Override global ul rules
 .forum-nav-browse-menu, .forum-nav-browse-submenu {
   margin: 0;
-  padding-left: 0;
 }
 
-// The sidebar class does a lot of things that we don't want in the thread list;
-// the following rules contain styling that is necessary and would otherwise
-// reside in elements/_navigation.scss if the sidebar styling did not make the
-// !important directive necessary.
-
-.forum-nav-browse-title {
-  border-bottom: 1px solid $gray-l3 !important;
-  padding: ($baseline/2) ($baseline/2) !important;
-
-  &:hover, &:focus {
-    background: $forum-color-active-thread !important;
-  }
-}
-
-.forum-nav-browse-submenu {
-  padding-left: $baseline !important;
+.forum-nav-browse-menu {
+  padding-left: 0;
 }
 
 // --------------------------------
@@ -99,48 +75,6 @@
 // navigation - thread list
 // --------------------------------
 
-// The sidebar class does a lot of things that we don't want in the thread list;
-// the following rules contain styling that is necessary and would otherwise
-// reside in elements/_navigation.scss if the sidebar styling did not make the
-// !important directive necessary.
-
-.forum-nav-thread {
-  background-color: $gray-l5 !important;
-
-  &.is-unread {
-    background-color: $white !important;
-  }
-}
-
-.forum-nav-thread-link {
-  padding: ($baseline/4) ($baseline/2) !important;
-
-  &.is-active, &:hover, &:focus {
-    background-color: $forum-color-active-thread !important;
-  }
-}
-
-li[class*=forum-nav-thread-label-] {
-  margin-top: ($baseline/4) !important;
-  padding: 1px 6px !important;
-}
-
-.forum-nav-load-more {
-  border-bottom: 1px solid $gray-l3 !important;
-  background-color: $gray-l5 !important;
-}
-
-.forum-nav-load-more-link {
-  &:hover, &:focus {
-    color: $link-color !important;
-    background-color: $forum-color-active-thread !important;
-  }
-}
-
-.forum-nav-load-more-link, .forum-nav-loading {
-  padding: $baseline 0 !important;
-}
-
 // The following rules would be unnecessary but for broadly scoped rules defined
 // elsewhere in our CSS.