Remove support for VectorOfVariables constraints

[blegat]

We recommend to only support a constraint if the solver has a native support for it (see this tip: https://jump.dev/JuMP.jl/stable/moi/tutorials/implementing/#Define-supports_constraint). The reason is that the bridging mechanism in MOI selects the bridges that minimize the number bridges needed to transform the user constraints into constraints supported by the solver. If the solver hardcodes some bridges then these transformations are not taken into account by the bridge shortest path heuristic. For instance, there are two bridges in SumOfSquares, a Kernel bridge which is best for solvers supporting PSD variables and equality constraints and an Image bridge which is best if the solver supports VectorAffineFunction-in-PSD. The bridge heuristic should use the Image bridge with Clarabel and the Kernel bridge if Clarabel is used with Dualization.jl. See https://youtu.be/CGPHaHxCG2w?t=590