docs: disable 2D board axes in 3D gallery examples #14

Job	Run time
Julia nightly - macOS-latest - aarch64	2m 51s
Julia nightly - ubuntu-latest - x64	2m 58s
Julia lts - ubuntu-latest - x64	2m 9s
Julia lts - windows-latest - x64	2m 50s
Julia nightly - windows-latest - x64	3m 44s
Julia 1 - ubuntu-latest - x64	3m 24s
Julia 1 - macOS-latest - aarch64	3m 24s
Julia lts - macOS-latest - aarch64	2m 40s
Julia 1 - windows-latest - x64	3m 28s
	27m 28s

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