chore: fix comment grammar mistake (vuejs#7739)

LarsStegman · yyx990803 · commit 68b51f2620a8 · 2018-03-08T12:21:57.000-05:00
diff --git a/src/core/observer/index.js b/src/core/observer/index.js
@@ -27,10 +27,10 @@ export const observerState = {
 }
 
 /**
- * Observer class that are attached to each observed
- * object. Once attached, the observer converts target
+ * Observer class that is attached to each observed
+ * object. Once attached, the observer converts the target
  * object's property keys into getter/setters that
- * collect dependencies and dispatches updates.
+ * collect dependencies and dispatch updates.
  */
 export class Observer {
   value: any;
