doc: rephrase text of child_process.execSync()

Rephrases the error thrown by child_process.execSync().

PR-URL: nodejs/node#14953
Fixes: nodejs/node#14944
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/child_process.md

@@ -685,8 +685,8 @@ does not exit, the parent process will still wait until the child process has
 exited.
 
 If the process times out, or has a non-zero exit code, this method ***will***
-throw.  The [`Error`][] object will contain the entire result from
-[`child_process.spawnSync()`][]
+throw an [`Error`][] that will include the full result of the underlying
+[`child_process.spawnSync()`][].
 
 ### child_process.execSync(command[, options])
 <!-- YAML