fix #2719: Remove tabindex

src/bootstrap-table.js

@@ -811,7 +811,6 @@
                     sprintf(' rowspan="%s"', column.rowspan),
                     sprintf(' colspan="%s"', column.colspan),
                     sprintf(' data-field="%s"', column.field),
-                    "tabindex='0'",
                     '>');
 
                 html.push(sprintf('<div class="th-inner %s">', that.options.sortable && column.sortable ?