Remove usage of extend from table SCSS

Should have no visual changes

app/assets/stylesheets/framework/tables.scss

@@ -23,6 +23,7 @@ table {
     @include gl-text-gray-500;
   }
 
+  .md &:not(.code),
   &.table {
     margin-bottom: $gl-padding;
 

app/assets/stylesheets/framework/typography.scss

@@ -160,8 +160,6 @@
   }
 
   table:not(.code) {
-    @extend .table;
-    @extend .table-bordered;
     margin: 16px 0;
     color: $gl-text-color;
     border: 0;
@@ -172,9 +170,11 @@
     tbody {
       background-color: $white;
 
-      td {
-        border-color: $gray-100;
-      }
+    }
+
+    td,
+    th {
+      border: 1px solid $border-color;
     }
 
     tr {