t4213: avoid "|" in sed regexp

Many versions of sed (e.g., that found on OS X) do not understand
"|"-alternation, even when backslash escaped.  Some versions can turn on
extended regexps with a special option, but of course that option is not
standard, either. Let's just write out our alternates longhand.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>