Clean up last 'enable' properties (#4364)

* Fix typo in setStackRoot animation docs

* Use 'enabled' instead of 'enable'

docs/docs/screen-api.md

@@ -62,7 +62,7 @@ Navigation.setStackRoot(this.props.componentId, {
         options: {
           animations: {
             setStackRoot: {
-              enable: true
+              enabled: true
             }
           }
         }

playground/src/screens/PushedScreen.js

@@ -111,7 +111,7 @@ class PushedScreen extends Component {
           },
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           },
           preview: {
@@ -178,7 +178,7 @@ class PushedScreen extends Component {
         options: {
           animations: {
             setStackRoot: {
-              enable: false
+              enabled: false
             }
           },
           topBar: {

playground/src/screens/WelcomeScreen.js

@@ -359,7 +359,7 @@ class WelcomeScreen extends Component {
         options: {
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           },
           preview: reactTag ? {
@@ -391,7 +391,7 @@ class WelcomeScreen extends Component {
         options: {
           animations: {
             push: {
-              enable: false
+              enabled: false
             }
           }
         }