Fix documentation for `childProcess.kill(signal)`: `signal` can be a number

[ehmicky]

With childProcess.kill(signal), signal is documented as being a string.

However in the code, signal can be either a string or a number.

[himself65]

I think the source code is here:

node/lib/internal/child_process.js

Lines 461 to 486 in 030fa2e

	ChildProcess.prototype.kill = function(sig) {
	const signal = sig === 0 ? sig :
	convertToValidSignal(sig === undefined ? 'SIGTERM' : sig);
	if (this._handle) {
	var err = this._handle.kill(signal);
	if (err === 0) {
	/* Success. */
	this.killed = true;
	return true;
	}
	if (err === UV_ESRCH) {
	/* Already dead. */
	} else if (err === UV_EINVAL || err === UV_ENOSYS) {
	/* The underlying platform doesn't support this signal. */
	throw errnoException(err, 'kill');
	} else {
	/* Other error, almost certainly EPERM. */
	this.emit('error', errnoException(err, 'kill'));
	}
	}
	/* Kill didn't succeed. */
	return false;
	};

[ZYSzys]

Fixed via #27760.