Add comments explaining why weak form is only for conserved terms

[DanielDoehring]

Closes #1671 .

[github-actions]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (fc00ac1) 93.24% compared to head (94aec1a) 96.09%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1676      +/-   ##
==========================================
+ Coverage   93.24%   96.09%   +2.84%     
==========================================
  Files         425      425              
  Lines       34378    34417      +39     
==========================================
+ Hits        32055    33070    +1015     
+ Misses       2323     1347     -976     

Flag	Coverage Δ
unittests	96.09% <ø> (+2.84%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/solvers/dg.jl	91.87% <ø> (ø)
src/solvers/dgsem_structured/dg_2d.jl	98.85% <ø> (ø)
src/solvers/dgsem_structured/dg_3d.jl	99.12% <ø> (ø)
src/solvers/dgsem_tree/dg_1d.jl	95.12% <ø> (ø)
src/solvers/dgsem_tree/dg_2d.jl	96.57% <ø> (ø)
src/solvers/dgsem_tree/dg_3d.jl	97.41% <ø> (ø)

... and 38 files with indirect coverage changes

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[andrewwinters5000]

Thanks for adding these comments throughout! I adjusted the wording slightly.

[ranocha]

Thanks for the PR! I just have one suggestion

[ranocha]

I also modified your post describing this PR. If you write something like

closes #number

or

fixes #number

GitHub will recognize it and close the issue automatically when the PR is merged.

[DanielDoehring]

I also modified your post describing this PR. If you write something like

closes #number

or

fixes #number

GitHub will recognize it and close the issue automatically when the PR is merged.

Ah interesting, I was not aware of this. Thanks for sharing!

[ranocha]

Thanks! Should be ready to be merged if @andrewwinters5000 agrees.

[andrewwinters5000]

LGTM!