Fix manifold value_gradient! call such that it returns both things.

[pkofod]

Fixes 1.9 for LineSearches v7.5.1. This fix is also appropriate for older versions of LineSearches as it should be the returned thing, but the ManifoldObjective wasnt used in the problematic manner so I'm not updating the bounds.

[devmotion]

I don't understand this PR. This issue was already fixed in [email protected] by #1213. Even if you would backport this fix to [email protected], then still all other existing releases < [email protected] would suffer from this problem: JuliaNLSolvers/LineSearches.jl#192

Either we just close JuliaNLSolvers/LineSearches.jl#192 and tell users to update to [email protected]. Or - since this might also not be an option for all users due to restrictions imposed by other dependencies - we update the registry to only allow LineSearches < 7.5.1 on Optim < 1.13.3. I don't think yanking [email protected] is an option, as that release is completely fine per se (the bug is an Optim bug in older releases) and development has moved on, using the same pattern in LineSearches, in subsequent releases.

[pkofod]

for some reason I got 1.9.4 when running something locally, but clearly that is not the last version prior to v2. My bad!