mailinfo: cleanup extra spaces for complex 'From:'

currently for cases like

From: A U Thor <a.u.thor@example.com> (Comment)

mailinfo extracts the following 'Author:' field:

Author: A U Thor   (Comment)
^^
which has two extra spaces left in there after removed email part.

I think this is wrong so here is a fix.

Signed-off-by: Kirill Smelkov <kirr@landau.phys.spbu.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>