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

[Kazu Hirata via cfe-commits]

================
@@ -206,23 +206,16 @@ Tracking the exact suspension point
 
 Among the compiler-generated members, the ``__coro_index`` is particularly
 important. This member identifies the suspension point at which the coroutine
-is currently suspended.
+is currently suspended. However, it is non-trivial to map this number backto
----------------
kazutakahirata wrote:

```suggestion
is currently suspended. However, it is non-trivial to map this number back to
```

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