skel: Do not set -o emacs in .shrc.

sh has defaulted to 'set -o emacs' since FreeBSD 9.0. Therefore, do not set
this again in .shrc, since that only serves to prevent invocations like
'sh -o vi' and 'sh +o emacs' to have the intended effect.

PR: 215958
Submitted by: Andras Farkas
MFC after: 1 week