Strided array doc: Remove reference to getindex (#26150)
* Strided array doc: Remove reference to getindex
As noticed by Jutho, we don't assume that `getindex(A, i)` is the same as accessing the `i`th element as computed by the strides.
* Rewrite with motivating examples...
instead of consise theoretical arithmetic.
* Emphasize the distinction from linear indexing
Co-authored-by: Tim Holy <tim.holy@gmail.com>
