chore: s/falsey/falsy (#3093)

public/_includes/_util-fns.jade

@@ -56,7 +56,7 @@
 
 //- Other
 - var _truthy = 'truthy';
-- var _falsey = 'falsey';
+- var _falsy = 'falsy';
 
 //- Used to prefix identifiers that are private. In Dart this will be '_'.
 - var _priv = '';

public/docs/ts/latest/guide/displaying-data.jade

@@ -1,7 +1,7 @@
 block includes
   include ../_util-fns
   - var _iterableUrl = 'https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols';
-  - var _boolean = 'truthy/falsey';
+  - var _boolean = 'truthy/falsy';
 
 :marked
   You can display data by binding controls in an HTML template to properties of an Angular component.

public/docs/ts/latest/guide/router.jade

@@ -2174,7 +2174,7 @@ a#CanDeactivate
   Notice that the `canDeactivate` method *can* return synchronously;
   it returns `true` immediately if there is no crisis or there are no pending changes.
   But it can also return a `Promise` or an `Observable` and the router will wait for that
-  to resolve to truthy (navigate) or falsey (stay put).
+  to resolve to truthy (navigate) or falsy (stay put).
 
 :marked
   Add the `Guard` to the crisis detail route in `crisis-center-routing.module.ts` using the `canDeactivate` array.

public/docs/ts/latest/guide/template-syntax.jade

@@ -671,7 +671,7 @@ code-example(format="nocode").
 :marked
   Finally, we can bind to a specific class name.
   Angular adds the class when the template expression evaluates to #{_truthy}.
-  It removes the class when the expression is #{_falsey}.
+  It removes the class when the expression is #{_falsy}.
 +makeExample('template-syntax/ts/app/app.component.html', 'class-binding-3')(format=".")
 
 .l-sub-section
@@ -828,7 +828,7 @@ block style-property-name-dart-diff
     [event propagation](https://developer.mozilla.org/en-US/docs/Web/API/Document_Object_Model/Examples#Example_5:_Event_Propagation)
     continues or stops with the current element.
 
-    Event propagation stops if the binding statement returns a falsey value (as does a method with no return value).
+    Event propagation stops if the binding statement returns a falsy value (as does a method with no return value).
     Clicking the button in the next example triggers a save;
     the click doesn't make it to the outer `<div>` so the div's save handler is not called.
   +makeExample('template-syntax/ts/app/app.component.html', 'event-binding-no-propagation')(format=".")
@@ -1052,10 +1052,10 @@ figure.image-display
     Don't forget the asterisk (`*`) in front of `ngIf`.
     For more information, see [\* and &lt;template>](#star-template).
 :marked
-  Binding to a #{_falsey} expression removes the element subtree from the DOM.
+  Binding to a #{_falsy} expression removes the element subtree from the DOM.
 +makeExample('template-syntax/ts/app/app.component.html', 'NgIf-2')(format=".")
 
-block dart-no-truthy-falsey
+block dart-no-truthy-falsy
   //- N/A
 
 :marked