test: do not test errinj.info() output

There is no much sense in testing it, but it is sensitive to source code
changes, especially `ERRINJ_*_COUNTDOWN` injections, e.g. see commit
697123d0 ("box: use maximal space id instead of _schema.max_id").

Needed for tarantool/tarantool-ee#712

NO_DOC=test
NO_CHANGELOG=test

(cherry picked from commit dc0fd81c)