test: remove unnecessary Buffer import

Removed require('buffer') from

- test/disabled/test-sendfd.js
- test/internet/test-dgram-broadcast-multi-process.js
- test/pummel/test-https-no-reader.js

PR-URL: https://github.com/nodejs/node/pull/13860
Refs: https://github.com/nodejs/node/issues/13836
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>

test/disabled/test-sendfd.js

@@ -29,12 +29,13 @@
 var common = require('../common');
 var assert = require('assert');
 
-var buffer = require('buffer');
-var child_process = require('child_process');
-var fs = require('fs');
-var net = require('net');
-var netBinding = process.binding('net');
-var path = require('path');
+const buffer = require('buffer');
+const child_process = require('child_process');
+const fs = require('fs');
+const net = require('net');
+
+const netBinding = process.binding('net');
+const path = require('path');
 
 var DATA = {
   'ppid' : process.pid,
@@ -91,7 +92,7 @@ var srv = net.createServer(function(s) {
   var str = JSON.stringify(DATA) + '\n';
 
   DATA.ord = DATA.ord + 1;
-  var buf = buffer.Buffer.allocUnsafe(str.length);
+  var buf = Buffer.allocUnsafe(str.length);
   buf.write(JSON.stringify(DATA) + '\n', 'utf8');
 
   s.write(str, 'utf8', pipeFDs[1]);

test/internet/test-dgram-broadcast-multi-process.js

@@ -4,7 +4,6 @@ const assert = require('assert');
 const dgram = require('dgram');
 const util = require('util');
 const networkInterfaces = require('os').networkInterfaces();
-const Buffer = require('buffer').Buffer;
 const fork = require('child_process').fork;
 const LOCAL_BROADCAST_HOST = '255.255.255.255';
 const TIMEOUT = common.platformTimeout(5000);

test/pummel/test-https-no-reader.js

@@ -8,7 +8,6 @@ if (!common.hasCrypto) {
 }
 const https = require('https');
 
-const Buffer = require('buffer').Buffer;
 const fs = require('fs');
 const path = require('path');