Simplify <excerpt> link function

Wrapping the init logic in `scope.$evalAsync()` used to be
necessary so that any code touching the '.excerpt' element
ran after that element had been transcluded into the DOM.

However, this is no longer necessary since all the init logic
now runs inside a `scope.$watch()` callback, which is invoked
after `ngIf` has inserted the '.excerpt' element into the DOM.

h/static/scripts/directive/excerpt.js

@@ -69,7 +69,6 @@ function excerpt($timeout) {
         return contentElem.scrollHeight > ctrl.collapsedHeight;
       };
 
-      scope.$evalAsync(function () {
       scope.$watch('vm.enabled()', function (isEnabled) {
         if (isEnabled) {
           contentElem = elem[0].querySelector('.excerpt');
@@ -101,7 +100,6 @@ function excerpt($timeout) {
           ctrl.onCollapsibleChanged({collapsible: ctrl.overflowing()});
         }
       });
-      });
     },
     scope: {
       /** Whether or not truncation should be enabled */