docs: correct typo 'specifity' to 'specificity'

Closes angular#4082

Author: Nick Mann

modules/angular2/src/core/render/dom/view/proto_view_merger.ts

@@ -283,7 +283,7 @@ function isWildcard(selector): boolean {
 // different sub views
 function sortContentElements(contentElements: Element[]): Element[] {
  // for now, only move the wildcard selector to the end.
- // TODO(tbosch): think about sorting by selector specifity...
+ // TODO(tbosch): think about sorting by selector specificity...
  var firstWildcard = null;
  var sorted = [];
  contentElements.forEach((contentElement) => {