port 2N gravity time step to Taal

[ranocha]

As discussed on Slack

[codecov]

Codecov Report

Merging #263 into dev will increase coverage by 0.00%.
The diff coverage is 91.30%.

@@           Coverage Diff           @@
##              dev     #263   +/-   ##
=======================================
  Coverage   87.57%   87.57%           
=======================================
  Files          66       66           
  Lines       11803    11826   +23     
=======================================
+ Hits        10336    10357   +21     
- Misses       1467     1469    +2     

Impacted Files	Coverage Δ
src/Trixi.jl	100.00% <ø> (ø)
src/semidiscretization_euler_gravity.jl	75.00% <91.30%> (+2.51%)	⬆️

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[sloede]

Thanks!