remove: drop Rust 1.76.0 MSRV from CI test matrix

- Remove 1.76.0 from test suite matrix as old version support not needed
- Keep 1.87.0, stable, and beta for comprehensive testing
- Simplifies CI pipeline by focusing on current Rust versions

Author: Tunglies

.github/workflows/ci.yml

@@ -20,7 +20,6 @@ jobs:
           - 1.87.0
           - stable
           - beta
-          - 1.76.0  # MSRV that supports Cargo.lock v4
     steps:
     - uses: actions/checkout@v4