Drop unnecessary Rust install in SemVer CI

In the last few days there was incompatibility of `cargo-semver-checks`
with the new stable Rust 1.93.0. While this should fixed by today's
release of `cargo-semver-checks`, we take the opportunity to drop an
unnecessary install step from the CI workflow, as the action will bring
their own Rust version if not configured otherwise.

Author: tnull

.github/workflows/semver.yml

@@ -7,9 +7,5 @@ jobs:
     steps:
       - name: Checkout source code
         uses: actions/checkout@v4
-      - name: Install Rust stable toolchain
-        run: |
-          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile=minimal --default-toolchain stable
-          rustup override set stable
       - name: Check SemVer
         uses: obi1kenobi/cargo-semver-checks-action@v2