Fix build on gcc v15 by updating highs-sys dependency

[alexdewar]

Description

The current version of highs-sys specified in Cargo.lock doesn't compile on gcc v15, but a new version with a fix has been released. As it's an indirect dependency (unlike the main highs crate), it won't be updated by dependabot, so we need to update it manually. I've done this by running cargo update.

Fixes #517.

Type of change

• Bug fix (non-breaking change to fix an issue)
• New feature (non-breaking change to add functionality)
• Refactoring (non-breaking, non-functional change to improve maintainability)
• Optimization (non-breaking change to speed up the code)
• Breaking change (whatever its nature)
• Documentation (improve or add documentation)

Key checklist

• All tests pass: $ cargo test
• The documentation builds and looks OK: $ cargo doc

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.79%. Comparing base (bbef385) to head (c166d87).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #608      +/-   ##
==========================================
+ Coverage   84.76%   84.79%   +0.03%     
==========================================
  Files          37       37              
  Lines        3301     3301              
  Branches     3301     3301              
==========================================
+ Hits         2798     2799       +1     
+ Misses        314      313       -1     
  Partials      189      189              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.