sequencer: actually translate report in do_exec()

sequencer: actually translate report in do_exec()

N_() is meant to be used on strings that are subsequently _()'d, which
isn't the case here.

The affected construct is a bit questionable from an i18n perspective,
as it pieces together a sentence from separate strings. However, it
doesn't appear to be that bad, as the "assembly instructions" are in a
translatable message as well. Lacking specific complaints from
translators, it doesn't seem worth changing this.

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>