test: remove redundant using in cctest

PR-URL: #14739
Reviewed-By: Refael Ackermann <[email protected]>
Reviewed-By: Daniel Bevenius <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Benjamin Gruenbaum <[email protected]>
Reviewed-By: Luigi Pinca <[email protected]>
Reviewed-By: Timothy Gu <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Alexey Orlenko <[email protected]>

Author: XadillaX

test/cctest/node_test_fixture.h

@@ -8,13 +8,6 @@
 #include "v8.h"
 #include "libplatform/libplatform.h"
 
-using node::Environment;
-using node::IsolateData;
-using node::CreateIsolateData;
-using node::CreateEnvironment;
-using node::AtExit;
-using node::RunAtExit;
-
 class ArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
  public:
   virtual void* Allocate(size_t length) {