bench: Update pinned nightly to 2026-08-06

This is the first version with LLVM23.

Author: tgross35

.github/workflows/main.yaml

@@ -15,7 +15,7 @@ env:
   RUSTDOCFLAGS: -Dwarnings
   RUSTFLAGS: -Dwarnings
   RUST_BACKTRACE: full
-  BENCHMARK_RUSTC: nightly-2026-08-05 # Pin the toolchain for reproducable results
+  BENCHMARK_RUSTC: nightly-2026-08-06 # Pin the toolchain for reproducable results
 
 defaults:
   run: