[5.9][CodeCompletion] Fix an issue that causes an iterator to be invalidated while iterating#66559

ahoppen merged 1 commit intoswiftlang:release/5.9swiftlang/swift:release/5.9from

ahoppen:ahoppen/5.9/iterator-invalidationahoppen/swift:ahoppen/5.9/iterator-invalidationCopy head branch name to clipboard