webdoc: rm GUI subsections from py reference

...content/py/sample/interference/grating/lattice1d/index.md

...le/interference/grating/lattice1d/interference_1d_gui.png

hugo/content/py/sample/interference/lattice2d/_index.md

...mple/interference/lattice2d/tutorial_interference_gui.png

hugo/content/py/sample/interference/para2d/index.md

...py/sample/interference/para2d/interference_para2d_gui.png

hugo/content/py/sample/interference/para_radial/index.md

...rference/para_radial/tutorial_interference_para1d_gui.png

hugo/content/py/sample/particle/distribution/_index.md