[llvm] [NFC][DebugInfo][RemoveDIs] Use iterators to insert in callsite-splitting (PR #74455)

[Jeremy Morse via llvm-commits]

jmorse wrote:

(added inline comment rather than deal with github further); an obvious fix is to perform this check before the call to eraseFromParent. I'll hold off on this as I've got too much in-flight right now.

https://github.com/llvm/llvm-project/pull/74455