Update SciMLTesting QA compat to 2.1

[ChrisRackauckas-Claude]

Ignore until reviewed by @ChrisRackauckas.

Summary

• Set test/qa SciMLTesting compat to exactly 2.1.

Validation

• timeout 3600 julia --project=test/qa --startup-file=no -e 'using Pkg; Pkg.instantiate(); include("test/qa/qa.jl")'\n- TOML parse check for test/qa/Project.toml\n- git diff --check\n- No changed Julia files for Runic\n- grep for api_docs = false, docstrings_broken, missing_docstrings, Base.Docs patterns

[ChrisRackauckas-Claude]

Local verification for a3fec9a:

• GROUP=QA timeout 3600 /home/crackauc/.juliaup/bin/julia +release --startup-file=no --project=. -e 'using Pkg; Pkg.test()'
  • resolved SciMLTesting v2.2.0
  • QA/qa.jl | 19 19 58.4s
  • Testing FiniteVolumeMethod1D tests passed
• git diff --check passed
• Runic not run because this patch changes only TOML compat files, not Julia files.

Note: the literal GROUP=QA timeout 3600 julia +release --startup-file=no --project=. -e 'using Pkg; Pkg.test()' invocation on this machine used /home/crackauc/.local/bin/julia, which does not support Juliaup channel selectors and failed before tests started by treating +release as a file path. I reran the same release-channel test through the Juliaup launcher shown above.