Fix `CodeGenerationFormat.formatChildrenSeparatedByNewline()` to not add an extra newline to the end of lists that already have one#2823

ahoppen merged 3 commits intoswiftlang:mainswiftlang/swift-syntax:mainfrom

roopekv:fix-extra-newline-after-code-gen-list-formatroopekv/swift-syntax:fix-extra-newline-after-code-gen-list-formatCopy head branch name to clipboard