Make ProvisionedDevices Optional

Fixes #7

Many profiles do not have an associated list of devices such as app-store profiles as once signed it works on any. This commit has been tested through 70 profiles on my machine hopefully testing most iOS situations (macOS is still a question mark).

Author: Sherlouk

Sources/SwiftyProvisioningProfile/Model/ProvisioningProfile.swift

@@ -41,7 +41,7 @@ public struct ProvisioningProfile: Codable {
     public var name: String
 
     /// An array of device UUIDs that are provisioned on this profile
-    public var provisionedDevices: [String]
+    public var provisionedDevices: [String]?
 
     /// An array of team identifier of which this profile belongs to
     public var teamIdentifiers: [String]