update lang/rust to 1.93.1
Announce: https://blog.rust-lang.org/2026/02/12/Rust-1.93.1/
Rust 1.93.1 resolves three regressions that were introduced in the 1.93.0 release.
- Don't try to recover a keyword as a non-keyword identifier, fixing an internal
compiler error (ICE) that especially affected rustfmt.
- Fix a clippy::panicking_unwrap false-positive on field access with an implicit
dereference.
- Revert an update to wasm-related dependencies, fixing file descriptor leaks on
the wasm32-wasip2 target. This only affects the rustup component for this
target, so downstream toolchain builds should check their own dependencies too.