test: revert fail `coverage` target if tests fail"

This reverts commit f216d5bb.
Seems like it breaks the nightly job so reverting until
we figure that out.

PR-URL: https://github.com/nodejs/node/pull/25543


Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>