[6.0] Switch to official 600.0.0 tag for swift-syntax (#708)#721

stmontgomery merged 1 commit intoswiftlang:release/6.0swiftlang/swift-testing:release/6.0from

stmontgomery:release/6.0/swift-syntax-600stmontgomery/swift-testing:release/6.0/swift-syntax-600Copy head branch name to clipboard