Remove orphan tableau test files from DiffEqDevTools

These tests were already moved to OrdinaryDiffEqExplicitTableaus and
OrdinaryDiffEqImplicitTableaus and are no longer included by
DiffEqDevTools runtests.jl.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: ChrisRackauckas