Allow Manopt 0.6 in OptimizationManopt

[ChrisRackauckas-Claude]

This PR should be ignored until reviewed by @ChrisRackauckas.\n\n## Summary\n- widens OptimizationManopt's Manopt compat from 0.5.25 to 0.5.25, 0.6\n- unblocks downstream Dependabot updates such as SciML/SymbolicAnalysis.jl#116, which otherwise continue resolving Manopt 0.5 because OptimizationManopt restricts Manopt to 0.5.x\n\n## Local verification\n- timeout 3600 /home/crackauc/.juliaup/bin/julia +1.10 --project=lib/OptimizationManopt -e 'using Pkg; Pkg.test()'\n - resolved Manopt v0.6.1, Manifolds v0.11.28, ManifoldsBase v2.4.0\n - result: Testing OptimizationManopt tests passed\n- timeout 3600 /home/crackauc/.juliaup/bin/julia +1.10 -e 'using Runic; exit(Runic.main(["--check", "."]))'\n - result: exit code 0\n\n## Downstream verification\nIn a local checkout of SciML/SymbolicAnalysis.jl at PR #116, I developed this local OptimizationManopt branch into the test environment and forced Manopt v0.6.1. The SymbolicAnalysis test entrypoint passed under that dependency set:\n\n- Manopt v0.6.1\n- Manifolds v0.11.28\n- OptimizationManopt v1.3.3 ../../Optimization.jl/lib/OptimizationManopt\n\nCommand used:\ntimeout 3600 /home/crackauc/.juliaup/bin/julia +1.10 --project=test -e 'using Pkg; Pkg.develop(PackageSpec(path=pwd())); Pkg.status(["SymbolicAnalysis", "Manopt", "OptimizationManopt", "Manifolds"]; mode=Pkg.PKGMODE_MANIFEST); include("test/runtests.jl")'\n\nResult: all SymbolicAnalysis test files passed, including Core/dgp.jl | 28 pass.