maxSdkVersion must be an integer

An @string resources is not a valid maxSdkVersion since all of the SDK version fields must be integers.

• https://gitlab.com/souch/SMSbypass/blob/v0.9/app/src/main/AndroidManifest.xml#L29
• https://gitlab.com/souch/SMSbypass/blob/v0.9/app/src/main/res/values/strings.xml#L27

The Android aapt interprets that as no maxSdkVersion.