[O] Optimize onclick method call

src/components/navigation/navigation.ts

@@ -183,13 +183,4 @@ export default class Navigation extends Vue
         if (this.selectedTime == 'All Year') return -1;
         else return +this.selectedTime.replace('Term ', '') - 1;
     }
-
-    /**
-     * This function is called when the sign out button is clicked.
-     */
-    public signOut()
-    {
-        // Call custom event
-        this.$emit('sign-out');
-    }
 }

src/components/navigation/navigation.vue

@@ -30,7 +30,7 @@
                 </el-dropdown-menu>
             </el-dropdown>
 
-            <el-button @click="signOut" id="sign-out-button" type="text">Sign Out</el-button>
+            <el-button @click="$emit('sign-out')" id="sign-out-button" type="text">Sign Out</el-button>
         </el-menu>
 
         <!-- Previous course / Next course (Only when the page is courses) -->