Update default Xcode version

fastlane/Fastfile

@@ -88,7 +88,7 @@ platform :ios do
     target_version = "Kingfisher-#{options[:version]}"
     
     swift_version = options[:swift_version] || "5.0"
-    xcode_version = options[:xcode_version] || "15.4"
+    xcode_version = options[:xcode_version] || "16.0"
 
     xcodes(version: xcode_version, select_for_current_build_only: true)
 
@@ -138,7 +138,7 @@ platform :ios do
   end
 
   before_all do |lane|
-    xcode_version = ENV["XCODE_VERSION"] || "15.4"
+    xcode_version = ENV["XCODE_VERSION"] || "16.0"
     xcodes(version: xcode_version, select_for_current_build_only: true)
   end