[FIX] web: IE <= 11.0 doesn't support ChildNode.remove

IE 11.0 doesn't support `Childnode.remove`:
http://caniuse.com/#feat=childnode-remove

As a workaround, we use `Node.removeChild`,
which is more widely supported.

opw-710617

addons/web/static/lib/qweb/qweb2.js

@@ -327,7 +327,8 @@ QWeb2.Engine = (function() {
                         if (self.tools.trim(text_node.nodeValue)) {
                             return self.tools.exception("Error: text is not allowed between branching directives");
                         }
-                        text_node.remove();
+                        // IE <= 11.0 doesn't support ChildNode.remove
+                        text_node.parentNode.removeChild(text_node);
                     }
                 } else {
                     return self.tools.exception("Error: t-elif and t-else directives must be preceded by a t-if or t-elif directive");