Update Small Grants (Completion): "Simple Handwritten PDEs as ODEs" Benchmark Set"

[GodotMisogi]

Alongside the completion of the task, a higher payout has been posted for voting, following discussion with the reviewers (@ChrisRackauckas). This is requested considering, in addition to the original task of fixing the benchmarks, the following:

1. Reformulations of the four PDE test problems to reflect more realistic benchmarks, along with their documentation.
2. Implementing better finite-difference and pseudospectral method implementations.
3. Extensive testing of the benchmarks with various solvers across the test problems.

[ChrisRackauckas]

This needs 2 more approvals because it also has a payout increase in it, but I think that's warranted since it wasn't just a bump of the benchmarks as mentioned but actually a complete overhaul which included setting up versions using all of the major new PDE tools (ClassicalOrthogonalPolynomials, SummationByPartsOperators, SciMLOperators) so it was a rather comprehensive overhaul, see SciML/SciMLBenchmarks.jl#1291.