src: trace_event macro line continuation cleanup

This commit makes the macro line continuations line up.

PR-URL: https://github.com/nodejs/node/pull/15750


Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>