Remove crubit todo about using //third_party/rust

crubit is part of the toolchain, so it has very different dependencies
than chromium does. We use upstream crates to build the toolchain,
including rustc, cargo, bindgen, etc.

R=lukasza@chromium.org

Bug: 40229252
Change-Id: Iaf324a1895df8b57f944d1ea86bca33181c5edab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5726076
Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Commit-Queue: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1330428}
NOKEYCHECK=True
GitOrigin-RevId: 758a505cef2396f7f889346eda963647b717fec2

Author: danakj

build_crubit.py

@@ -97,7 +97,6 @@ def CheckoutCrubit(commit, dir):
 def BuildCrubit(build_mac_arm):
     # TODO(crbug.com/40229251): Use locally built Rust instead of having
     # Bazel always download the whole Rust toolchain from the internet.
-    # TODO(crbug.com/40229252): Use crates from chromium/src/third_party/rust.
 
     # This environment variable is consumed by crubit/bazel/llvm.bzl and will
     # configure Crubit's build to include and link against LLVM+Clang headers