Fix declaration of "_installMode" to remove warnings

[newyankeecodeshop]

The _installMode property should not be declared as a pointer since it holds an enum value. This code causes Xcode to display the following warnings:

Showing All Issues
.../node_modules/react-native-code-push/ios/CodePush/CodePush.m:591:22: Comparison between pointer and integer ('CodePushInstallMode *' (aka 'enum CodePushInstallMode *') and 'NSInteger' (aka 'long'))
.../node_modules/react-native-code-push/ios/CodePush/CodePush.m:775:22: Incompatible integer to pointer conversion assigning to 'CodePushInstallMode *' (aka 'enum CodePushInstallMode *') from 'CodePushInstallMode' (aka 'enum CodePushInstallMode'); take the address with &

[msftclas]

This seems like a small (but important) contribution, so no Contribution License Agreement is required at this point. We will now review your pull request.
Thanks,
Microsoft Pull Request Bot

[max-mironov]

@newyankeecodeshop good catch and thanks for contribution! Merging this.