ci: use nightly toolchain for cargo udeps

Author: NickLarsenNZ

.github/workflows/build.yml

@@ -61,7 +61,7 @@ jobs:
           key: udeps
           cache-all-crates: "true"
       - uses: stackabletech/cargo-install-action@cargo-udeps
-      - run: cargo udeps --workspace --all-targets
+      - run: cargo "+$RUST_NIGHTLY_TOOLCHAIN_VERSION" udeps --workspace --all-targets
 
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