Update backtrace submodule
This pulls in a few notable changes (see the [complete list](99faef833f...e9da96eb45
) for details):
- https://github.com/rust-lang/backtrace-rs/pull/508
- https://github.com/rust-lang/backtrace-rs/pull/566
- https://github.com/rust-lang/backtrace-rs/pull/569
- Fixes #116403 by no longer using `dbghelp.dll` during backtrace capture.