Revert "ci: Pin nightly toolchain for sanitizers to nightly-2024-03-13"

This reverts commit ac4e23f.

Author: taiki-e

.github/workflows/ci.yml

@@ -256,8 +256,7 @@ jobs:
     steps:
       - uses: taiki-e/checkout-action@v1
       - name: Install Rust
-        # TODO: LLVM bug https://github.com/rust-lang/rust/issues/122476
-        run: rustup toolchain install nightly-2024-03-13 --component rust-src && rustup default nightly-2024-03-13
+        run: rustup toolchain install nightly --component rust-src && rustup default nightly
       # https://github.com/google/sanitizers/issues/1716 / https://github.com/actions/runner-images/issues/9491
       - run: sudo sysctl vm.mmap_rnd_bits=28
       - run: cargo -Z build-std test --workspace --all-features --target x86_64-unknown-linux-gnu --lib --tests