doc: fix broken link for ChildProcess

Fixes: #36787
Signed-off-by: James M Snell <jasnell@gmail.com>

PR-URL: #36788
Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Juan José Arboleda <soyjuanarbol@gmail.com>

Author: jasnell

doc/api/child_process.md

@@ -1655,7 +1655,7 @@ or [`child_process.fork()`][].
 [`'error'`]: #child_process_event_error
 [`'exit'`]: #child_process_event_exit
 [`'message'`]: process.md#process_event_message
-[`ChildProcess`]: #child_process_child_process
+[`ChildProcess`]: #child_process_class_childprocess
 [`Error`]: errors.md#errors_class_error
 [`EventEmitter`]: events.md#events_class_eventemitter
 [`child_process.exec()`]: #child_process_child_process_exec_command_options_callback