fix: cargo-deny failure due to toolchain not installed (#4127)

example: https://github.com/dfinity/sdk/actions/runs/13636726972/job/38121248105?pr=4126

Author: ericswanson-dfinity

.github/workflows/deny.yml

@@ -22,6 +22,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
+      - run: rm rust-toolchain.toml
       - uses: EmbarkStudios/cargo-deny-action@v1
         with:
           command: check bans licenses sources # skip advisories, which are handled by audit.yml