Revert "css: remove table bottom margin from both css and scss"

This reverts commit 4b3d241d.
CSS complexity, right?  This isn't needed anymore.

src/opnsense/www/themes/opnsense/assets/stylesheets/bootstrap/_tables.scss

@@ -17,6 +17,7 @@ th {
 .table {
   width: 100%;
   max-width: 100%;
+  margin-bottom: $line-height-computed;
   // Cells
   > thead,
   > tbody,

src/opnsense/www/themes/opnsense/build/css/main.css

@@ -2020,7 +2020,8 @@ th {
 
 .table {
   width: 100%;
-  max-width: 100%; }
+  max-width: 100%;
+  margin-bottom: 20px; }
   .table > thead > tr > th,
   .table > thead > tr > td,
   .table > tbody > tr > th,