Convert path-form deps to URL-form (resolve URL→global mirror)

All .package(path: "../…") sibling deps → .package(url: "https://github.com/<org>/<repo>.git", branch: "main").
Per [RELEASE-015]; package identity preserved via the global mirror (local-dir basename), so consumer .product(package:) refs are unchanged. Local builds unaffected.

Author: coenttb

Package.swift

@@ -14,9 +14,9 @@ let package = Package(
         .library(name: "Sockets Standard", targets: ["Sockets Standard"])
     ],
     dependencies: [
-        .package(path: "../../swift-ietf/swift-rfc-768"),
-        .package(path: "../../swift-ietf/swift-rfc-791"),
-        .package(path: "../../swift-ietf/swift-rfc-9293")
+        .package(url: "https://github.com/swift-ietf/swift-rfc-768.git", branch: "main"),
+        .package(url: "https://github.com/swift-ietf/swift-rfc-791.git", branch: "main"),
+        .package(url: "https://github.com/swift-ietf/swift-rfc-9293.git", branch: "main")
     ],
     targets: [
         .target(