[FIX] component: do not validate props twice

it is not useful to do it in the component directive, especially since
it is done in the constructor, and the default props are not applied.

closes #379

src/component/directive.ts

@@ -412,9 +412,6 @@ QWeb.addDirective({
     ctx.addLine(
       `if (!W${componentID}) {throw new Error('Cannot find the definition of component "' + componentKey${componentID} + '"')}`
     );
-    if (QWeb.dev) {
-      ctx.addLine(`utils.validateProps(W${componentID}, props${componentID})`);
-    }
     ctx.addLine(`w${componentID} = new W${componentID}(parent, props${componentID});`);
     ctx.addLine(`parent.__owl__.cmap[${templateId}] = w${componentID}.__owl__.id;`);