refactor(ios): remove unused method, cordovaVersion

[kumo01GitHub]

Platforms affected

iOS, browser

Motivation and Context

Cordova version is set in Objective-C and JavaScript but only use JavaScript as README.

The version information comes from the cordova.js file.

Description

Remove Objective-C method.

Testing

Tested with Simulator.

Checklist

• I've run the tests to see all new and existing tests pass
• I added automated test coverage as appropriate for this change
• Commit is prefixed with (platform) if this change only applies to one platform (e.g. (android))
• If this Pull Request resolves an issue, I linked to the issue in the text above (and used the correct keyword to close issues using keywords)
• I've updated the documentation if necessary

[kumo01GitHub]

related issue #101

I saw the comment but device.js doesn't refer to info.cordova.

(Note: https://issues.apache.org/jira/browse/CB-5105 says "iOS is doing something special, but doing it right, so don't make any changes to iOS." but no idea what that refers to)

cordova-plugin-device/www/device.js

Line 55 in 8685a7a

var buildLabel = cordova.version;