Update README.md to remove old iOS options paragraph

[alexcroox]

• There is a full range of iOS options available now

[alexcroox]

cc @dennisameling as this was your original change

[dennisameling]

@alexcroox I added that line because it is in fact true that Apple only officially supports UIApplication.openSettingsURLString which equals the IOSSettings.App option in this plugin. Using any other option is at your own risk as Apple might reject your app from the store or break this functionality in future iOS updates. Please refer to https://stackoverflow.com/a/34024467/4337765 for details.

If you have a suggestion for a better wording of this sentence, I'm all for it 😊

[alexcroox]

Ah my bad I thought it was a line from the old version that wasn’t true anymore since the introduction of the newly supported options. I will steer clear of using them then!