use direct-child selector more in table styles to better support nested tables; fixes #10231

less/tables.less

@@ -18,9 +18,9 @@ th {
   width: 100%;
   margin-bottom: @line-height-computed;
   // Cells
-  thead,
-  tbody,
-  tfoot {
+  > thead,
+  > tbody,
+  > tfoot {
     > tr {
       > th,
       > td {
@@ -32,22 +32,23 @@ th {
     }
   }
   // Bottom align for column headings
-  thead > tr > th {
+  > thead > tr > th {
     vertical-align: bottom;
     border-bottom: 2px solid @table-border-color;
   }
   // Remove top border from thead by default
-  caption + thead,
-  colgroup + thead,
-  thead:first-child {
-    tr:first-child {
-      th, td {
+  > caption + thead,
+  > colgroup + thead,
+  > thead:first-child {
+    > tr:first-child {
+      > th,
+      > td {
         border-top: 0;
       }
     }
   }
   // Account for multiple tbody instances
-  tbody + tbody {
+  > tbody + tbody {
     border-top: 2px solid @table-border-color;
   }
 
@@ -61,9 +62,9 @@ th {
 // Condensed table w/ half padding
 
 .table-condensed {
-  thead,
-  tbody,
-  tfoot {
+  > thead,
+  > tbody,
+  > tfoot {
     > tr {
       > th,
       > td {