Update swift-syntax dependency upper bound to support version 603.x

Author: qizh

Package.swift

@@ -20,7 +20,7 @@ let package = Package(
         .plugin(name: "MetaProtocolCodable", targets: ["MetaProtocolCodable"]),
     ],
     dependencies: [
-        .package(url: "https://github.com/swiftlang/swift-syntax.git", "509.1.0"..<"603.0.0"),
+        .package(url: "https://github.com/swiftlang/swift-syntax.git", "509.1.0"..<"604.0.0"),
         .package(url: "https://github.com/apple/swift-collections.git", from: "1.0.4"),
         .package(url: "https://github.com/apple/swift-argument-parser.git", from: "1.2.2"),
         .package(url: "https://github.com/swiftlang/swift-docc-plugin", from: "1.0.0"),