[clang] [docs][coroutines] Update gdb debugger script (PR #162145)

[Chuanqi Xu via cfe-commits]

https://github.com/ChuanqiXu9 approved this pull request.

TBH, I don't have time to understand the script line by line right now (I am not so familar with the gdb script, I just wrote it by reading the document) but I think it is worthy to trust @vogelsgesang 

https://github.com/llvm/llvm-project/pull/162145