Update credentials-verification.yml (#3436)

According to [these
docs](https://doc.rust-lang.org/cargo/reference/config.html?highlight=CARGO_REGISTRY_TOKEN#credentials),
we should be able to just set an env var instead of calling `cargo
login`.

----

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.github/workflows/credentials-verification.yml

@@ -16,9 +16,8 @@ jobs:
     - name: Verify Crates.io Token
       shell: bash
       env:
-        RELEASE_AUTOMATION_BOT_CRATESIO_TOKEN: ${{ secrets.RELEASE_AUTOMATION_BOT_CRATESIO_TOKEN }}
+        CARGO_REGISTRY_TOKEN: ${{ secrets.RELEASE_AUTOMATION_BOT_CRATESIO_TOKEN }}
       run: |
-        cargo login "${RELEASE_AUTOMATION_BOT_CRATESIO_TOKEN}"
         echo "Checking cargo auth token..."
         # "cargo login" only saves a token and does not actually use it, so we use "cargo yank" to verify the token.
         # This version has already been yanked, so it is safe to execute the command below repeatedly.