allow arm64 building with newer sparkle framework

[reaperhulk]

This PR does the following:

• Bumps the bundled sparkle to 1.24.0. This is a universal framework compatible with both x86_64 and arm64.
• Removes the arm64 exclusion from the xcode project
• Changes the sparkle update feed from http://www.abyssoft.com/software/teleport/version.plist to https://invalid.invalid. This is objectively a terrible thing to do, but the updated Sparkle framework (correctly) raises a modal dialog on launch saying it won't communicate with an insecure origin if you don't supply an https URL. the invalid TLD is reserved in RFC 2606 so we can be sure that will always result in a lookup failure provided the DNS provider isn't deliberately wrecking NXDOMAIN responses. Since the old feed isn't working anyway this is just a crappy workaround for now until #57 can be addressed.

These changes allow arm64 to build and work for me, but I am not normally an objc developer so it's quite possible I've done something very dumb here.

[johndbritton]

I just released v1.2.3 with these changes.