CMake: Set macOS deployment options on ladybird to quiet Xcode

[ADKaster]

When using the Xcode generator, Xcode complains about a mismatch between CMake and the plist file for the application name.

It also complains that we're not using codesign properly, so just disable codesign altogether.

Note that actually using -GXcode for cmake won't work without https://github.com/SerenityOS/serenity/pull/15659