t: avoid alternation (not POSIX) in grep's BRE
f1e3df3169 (t: increase test coverage of signature verification output,
2020-03-04) adds GPG dependent tests to t4202 and t6200 that were found
problematic with at least OpenBSD 6.7.
Using an escaped '|' for alternations works only in some implementations
of grep (e.g. GNU and busybox).
It is not part of POSIX[1] and not supported by some BSD, macOS, and
possibly other POSIX compatible implementations.
Use `grep -E`, and write it using extended regular expression.
[1] https://pubs.opengroup.org/onlinepubs/
9699919799/basedefs/V1_chap09.html#tag_09_03
Helped-by: Torsten Bögershausen <tboegi@web.de>
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>