Fixes #11623: Reset position to static for grid columns within tables to unfuck borders in IE9/10 and Firefox

dist/css/bootstrap.css

@@ -1719,6 +1719,7 @@ th {
 }
 
 table col[class*="col-"] {
+  position: static;
   display: table-column;
   float: none;
 }

less/tables.less

@@ -133,6 +133,7 @@ th {
 // Reset default table behavior
 
 table col[class*="col-"] {
+  position: static; // Prevent border hiding in Firefox and IE9/10 (see https://github.com/twbs/bootstrap/issues/11623)
   float: none;
   display: table-column;
 }