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

[Adrian Vogelsgesang via cfe-commits]

vogelsgesang wrote:

> so let me just proofread the documentation changes.

Thank you! Fixed

> I'm not familiar with the gdb script

Let's see if @ChuanqiXu9 (afaik, the author of the previous gdb script) has any feedback on the script itself 🙂 

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