igloo: drop the render options the former renderer left behind

GraphRenderOptions.interaction has no reader left, and both of its
writers only ever set it to false. GraphRenderOptionsVS declared
editing, which the model dropped along with the renderer, and
interaction beside it.

Neither key is translated anywhere: the dashboard REST model maps
neither, the views valuespec offers neither, and a stored dashlet
carrying one reaches the model through model_validate, which ignores
what the model does not declare.

JIRA-Ref: CMK-37237
Change-Id: I67be47914b832393dc5309b3174203e2c3e79889