Remove incorrect getter for DualObjectiveValue #375

Job	Run time
Julia 1 - windows-latest - x64 - pull_request	13m 9s
Julia 1.10 - windows-latest - x64 - pull_request	9m 21s
Julia 1.10 - ubuntu-latest - x64 - pull_request	8m 20s
Julia 1.10 - ubuntu-latest - x86 - pull_request	9m 10s
Julia 1 - macos-14 - aarch64 - pull_request	6m 32s
Julia 1 - macOS-latest - x64 - pull_request	12m 24s
Julia 1.10 - macOS-latest - x64 - pull_request	11m 3s
Julia 1 - ubuntu-latest - x64 - pull_request	11m 48s
	1h 21m 47s

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