Clean up last 'enable' properties (#4364)

* Fix typo in setStackRoot animation docs

* Use 'enabled' instead of 'enable'

docs/docs/screen-api.md

         options: {
           animations: {
             setStackRoot: {
-              enable: true
+              enabled: true
             }
           }
         }

playground/src/screens/PushedScreen.js

           },
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           },
           preview: {
         options: {
           animations: {
             setStackRoot: {
-              enable: false
+              enabled: false
             }
           },
           topBar: {

playground/src/screens/WelcomeScreen.js

         options: {
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           },
           preview: reactTag ? {
         options: {
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           }
         }