doc: update description of 'clientError' event
Default behavior is to send a '400 Bad Request' response if the socket is writable.
Refs: https://github.com/nodejs/node/pull/15324
Checklist
-
make -j4 test
(UNIX), orvcbuild test
(Windows) passes -
documentation is changed or added -
commit message follows commit guidelines
Affected core subsystem(s)
doc