Fixed docs for return values of scipy.sparse.linalg.eigsh

v[:, i] (not v[i]) is indeed the eigenvector corresponding to w[i].
The docstring for eigs, also given in this file, is already correct.
Merge pull request #2915 from garrison/eigsh-doc-patch

DOC: sparse.linalg: fixed docs for return values of scipy.sparse.linalg.eigsh