Fix warnings with Julia 1.12

[oyamad]

Warning messages during precompilation:

┌ LRSLib
│  WARNING: Constructor for type "HRepresentation" was extended in `LRSLib` without explicit qualification or import.
│    NOTE: Assumed "HRepresentation" refers to `Polyhedra.HRepresentation`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function HRepresentation end`.
│    Hint: To silence the warning, qualify `HRepresentation` as `Polyhedra.HRepresentation` in the method signature or explicitly `import Polyhedra: HRepresentation`.
│  WARNING: Constructor for type "LiftedHRepresentation" was extended in `LRSLib` without explicit qualification or import.
│    NOTE: Assumed "LiftedHRepresentation" refers to `Polyhedra.LiftedHRepresentation`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function LiftedHRepresentation end`.
│    Hint: To silence the warning, qualify `LiftedHRepresentation` as `Polyhedra.LiftedHRepresentation` in the method signature or explicitly `import Polyhedra: LiftedHRepresentation`.
│  WARNING: Constructor for type "VRepresentation" was extended in `LRSLib` without explicit qualification or import.
│    NOTE: Assumed "VRepresentation" refers to `Polyhedra.VRepresentation`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function VRepresentation end`.
│    Hint: To silence the warning, qualify `VRepresentation` as `Polyhedra.VRepresentation` in the method signature or explicitly `import Polyhedra: VRepresentation`.
│  WARNING: Constructor for type "LiftedVRepresentation" was extended in `LRSLib` without explicit qualification or import.
│    NOTE: Assumed "LiftedVRepresentation" refers to `Polyhedra.LiftedVRepresentation`. This behavior is deprecated and may differ in future versions.`
│    NOTE: This behavior may have differed in Julia versions prior to 1.12.
│    Hint: If you intended to create a new generic function of the same name, use `function LiftedVRepresentation end`.
│    Hint: To silence the warning, qualify `LiftedVRepresentation` as `Polyhedra.LiftedVRepresentation` in the method signature or explicitly `import Polyhedra: LiftedVRepresentation`.
└  

[blegat]

I guess we should just explicitly prefix it, I think it's good practice anyway