Fix StiffODE benchmark by removing broken GeometricIntegratorsDiffEq dependency

[ChrisRackauckas-Claude]

Summary

This PR fixes the StiffODE benchmark by removing the broken GeometricIntegratorsDiffEq dependency.

Problem

GeometricIntegratorsDiffEq fails to precompile with Julia 1.11 due to type errors in the underlying GeometricIntegrators package:

ERROR: LoadError: TypeError: in Type{...} expression, expected UnionAll, got Type{SimpleSolvers.NonlinearSolver}

Root Cause

The GeometricIntegratorsDiffEq dependency was not actively used in the StiffODE benchmarks. All usages were commented out with notes indicating it has not been upgraded to modern Julia versions (see comments in ROBER.jmd line 37: "GeometricIntegratorsDiffEq has not upgraded to Julia 1.0").

Changes

• Removed GeometricIntegratorsDiffEq from StiffODE Project.toml deps
• Removed GeometricIntegratorsDiffEq from StiffODE Project.toml compat
• Regenerated Manifest.toml for StiffODE benchmark

Testing

• ✅ Verified StiffODE benchmark instantiates successfully after fix
• ✅ Verified NonStiffODE benchmark still works
• ✅ Verified NonlinearProblem benchmark still works
• ✅ Verified Jumps benchmark still works

Files Checked

All usages of GeometricIntegratorsDiffEq in StiffODE benchmarks are commented out:

• StiffODE/VanDerPol.jmd:48:#using GeometricIntegratorsDiffEq
• StiffODE/ROBER.jmd:43:#using GeometricIntegratorsDiffEq
• StiffODE/Hires.jmd:59:#using GeometricIntegratorsDiffEq
• StiffODE/Orego.jmd:46:#using GeometricIntegratorsDiffEq
• StiffODE/Pollution.jmd:228:#using GeometricIntegratorsDiffEq

cc @ChrisRackauckas