ci: remove nightly args from msrv

Author: CosminPerRam

.github/workflows/ci.yml

@@ -61,9 +61,9 @@ jobs:
       - uses: actions/checkout@v4
       - name: Install Rust (rustup)
         run: |
-          rustup toolchain install ${version} nightly --profile minimal --no-self-update
+          rustup toolchain install ${version} --profile minimal --no-self-update
           rustup default ${version}
-          cargo +nightly update -Zminimal-versions
+          cargo update -Zminimal-versions
         shell: bash
       - run: cargo build
       - run: cargo build --all-features