Fix Rust version in Github Actions

This is to ensure that an update of the Rust language does not cause CI
to fail, due to new lints. The Rust version available for the last
commit on `master` is 1.76.0, therefore CI uses that.

With this change an update of the Rust version does not break things.

.github/workflows/ci.yml

@@ -25,16 +25,19 @@ jobs:
           - runs-on: macos-latest
     steps:
       - uses: actions/checkout@v4
-      - uses: dtolnay/rust-toolchain@stable
+      - uses: actions-rust-lang/setup-rust-toolchain@v1
+        with:
+          toolchain: 1.76.0
       - run: cargo test -- --skip args::args_tests::update_config_test_color_choice::case_4 --skip test_package
 
   clippy:
     name: Check that clippy is happy
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: actions-rust-lang/setup-rust-toolchain@v1
       with:
+        toolchain: 1.76.0
         components: clippy
     - run: cargo clippy --workspace --all-features --all-targets --no-deps -- -D warnings
 
@@ -43,7 +46,8 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: actions-rust-lang/setup-rust-toolchain@v1
       with:
+        toolchain: 1.76.0
         components: rustfmt
     - run: cargo fmt --all -- --check