fix: test: Fix failing grep invocation on OpenBSD

Lines starting with A or NSEC are expected but not matched with the
OpenBSD grep. Extended regular expressions with direct use of
parentheses and the pipe symbol is more appropriate.

    I:checking RRSIG query from cache (154)
    I:failed

The issue appeared in #4805.

Merge branch 'mnowak/openbsd-grep-fix' into 'main'

See merge request isc-projects/bind9!10285