src: remove unnecessary std::endl usage

This commit removes a few std::endl that could be replaced by '\n' as it
does not look like the buffer needs to be flushed in these places.

This is only done in error handling, and once when the report has been
generated, so this is very minor but I thought I'd bring it up in case
it was overlooked.

PR-URL: https://github.com/nodejs/node/pull/30003


Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>