Change dependency on swift-tools-support-core to release/6.0

Author: ahoppen

Package.swift

@@ -160,7 +160,7 @@ if ProcessInfo.processInfo.environment["SWIFT_DRIVER_LLBUILD_FWK"] == nil {
 
 if ProcessInfo.processInfo.environment["SWIFTCI_USE_LOCAL_DEPS"] == nil {
   package.dependencies += [
-    .package(url: "https://github.com/apple/swift-tools-support-core.git", branch: "main"),
+    .package(url: "https://github.com/apple/swift-tools-support-core.git", branch: "release/6.0"),
     .package(url: "https://github.com/jpsim/Yams.git", .upToNextMinor(from: "5.0.0")),
     // The 'swift-argument-parser' version declared here must match that
     // used by 'swift-package-manager' and 'sourcekit-lsp'. Please coordinate