ci: add missing install "cargo-no-std-check"

Author: n-prat

.github/workflows/rust.yml

@@ -47,4 +47,5 @@ jobs:
         override: true
     - name: build
       run: >
-         cargo no-std-check --no-default-features --features=num-traits
+        cargo install cargo-no-std-check
+        cargo no-std-check --no-default-features --features=num-traits