mathlib3

7e6b8a9d - feat(linear_algebra/affine_space/basic): more vector_span lemmas (#3866)

feat(linear_algebra/affine_space/basic): more vector_span lemmas (#3866) Add more lemmas relating `vector_span` to the `submodule.span` of particular subtractions of points. The new lemmas fix one of the points in the subtraction and exclude that point, or its index in the case of an indexed family of points rather than a set, from being on the other side of the subtraction (whereas the previous lemmas don't exclude the trivial subtraction of a point from itself).