Add rust edition parameter to CI

.github/workflows/ci.yml

@@ -183,7 +183,7 @@ jobs:
       # We use a synthetic crate to ensure no dev-dependencies are enabled, which can
       # be incompatible with some of these targets.
       - name: Create synthetic crate for testing
-        run: cargo init --lib ci-build
+        run: cargo init --lib  --edition 2021 ci-build
       - name: Copy Rust version into synthetic crate
         run: cp crates/rust-toolchain.toml ci-build/
       - name: Copy patch directives into synthetic crate