test: remove `require('buffer')` from 4 test files

We don't use the global Buffer throughout the lib/ to avoid circular
dependency issues in core, but we actually don't need to require it on
test files. So remove them on:

+ test/parallel/test-stream-uint8array.js
+ test/parallel/test-stream2-finish-pipe.js
+ test/parallel/test-tls-session-cache.js
+ test/parallel/test-vm-cached-data.js

Refs: https://github.com/nodejs/node/issues/13836
PR-URL: https://github.com/nodejs/node/pull/13844
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Alexey Orlenko <eaglexrlnk@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/test/parallel/test-stream-uint8array.js b/test/parallel/test-stream-uint8array.js
index 1b02c55d97..38a45d5404 100644
--- a/test/parallel/test-stream-uint8array.js
+++ b/test/parallel/test-stream-uint8array.js
@@ -1,7 +1,6 @@
 'use strict';
 const common = require('../common');
 const assert = require('assert');
-const Buffer = require('buffer').Buffer;
 
 const { Readable, Writable } = require('stream');