Fix a11y issues.

TNL-6440, TNL-6439

lms/static/sass/course/base/_base.scss

@@ -59,7 +59,6 @@ table {
 
 a {
   &:hover, &:focus {
-    color: $pink;
     text-decoration: none !important;
   }
 }

lms/static/sass/course/wiki/_wiki.scss

@@ -8,6 +8,11 @@
     float: right;
   }
 
+  .form-search .input-prepend>label {
+    display: inline-block;
+    vertical-align: bottom;
+  }
+
   @include clearfix();
 
   .breadcrumbs-header {
@@ -746,17 +751,9 @@
   }
 
   .filter-clear {
-    margin-right: ($baseline/2);
+    margin-left: ($baseline/2);
     margin-top: ($baseline/2);
     font-size: .9em;
-
-    a {
-      color: $uxpl-gray-base;
-
-      &:hover, &:focus {
-        color: #777;
-      }
-    }
   }
 
   .table.table-striped {
@@ -773,6 +770,12 @@
       margin-left: 3px;
     }
 
+    a {
+      &:hover, &:focus {
+        font-weight: bold;
+      }
+    }
+
     tr:nth-child(even) {
       background: $gray-l6;
     }