Rename gravity_constant to gravity in the equations constructor

[patrickersing]

This PR renames the gravity_constant keyword in the equations constructor to gravity and fixes the docstrings/comments to describe this quantity as the gravitational acceleration instead of the gravitational constant. This will make it consistent with the actual field equations.gravity and avoid any confusion between gravitational acceleration and the gravitational constant. See trixi-framework/TrixiShallowWater.jl#82, trixi-framework/TrixiShallowWater.jl#84.

Since this changes the keyword argument for the equations constructor it must be considered a breaking change.

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.93%. Comparing base (f76ccaf) to head (da986a3).
Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2357   +/-   ##
=======================================
  Coverage   96.93%   96.93%           
=======================================
  Files         500      500           
  Lines       41499    41499           
=======================================
  Hits        40226    40226           
  Misses       1273     1273           

Flag	Coverage Δ
unittests	96.93% <100.00%> (ø)

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[DanielDoehring]

Breaking changes should be documented in the News.md :)

[patrickersing]

Breaking changes should be documented in the News.md :)

I have now added the respective entry to the News.md in c0b2ba7.

[DanielDoehring]

Looks ok from the technical side, but someone else should give the final verdict here.

[andrewwinters5000]

LGTM! I added this to the list of the PRs for the next breaking release

[ranocha]

Thanks. I marked this as a draft so that nobody accidentally merges it before we are prepared for the next breaking release.