[ci] Roll pinned nightly toolchain (#684)

Author: google-pr-creation-bot

Cargo.toml

@@ -31,7 +31,7 @@ rustdoc-args = ["--cfg", "doc_cfg", "--generate-link-to-definition"]
 [package.metadata.ci]
 # The versions of the stable and nightly compiler toolchains to use in CI.
 pinned-stable = "1.74.0"
-pinned-nightly = "nightly-2023-12-05"
+pinned-nightly = "nightly-2023-12-06"
 
 [package.metadata.playground]
 features = ["__internal_use_only_features_that_work_on_stable"]