src: remove unused isolate variable

[danbev]

Currently the following compiler warning is generated:

../src/node_task_queue.cc:93:12: warning:
unused variable 'isolate' [-Wunused-variable]
  Isolate* isolate = env->isolate();
           ^
1 warning generated.

This commit removes the unused variable.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[nodejs-github-bot]

@danbev build started: https://ci.nodejs.org/blue/organizations/jenkins/node-test-pull-request-lite-pipeline/detail/node-test-pull-request-lite-pipeline/2154/pipeline

[danbev]

CI: https://ci.nodejs.org/job/node-test-pull-request/19955/

[cjihrig]

FWIW, I'm in favor of fast tracking trivial compiler warning fixes like this one.

[danbev]

Please +1 for fast tracking.

[addaleax]

Landed in 398916a

[starkwang]

This change seems no need to be backported. The removed isolate variable is being used in here:

node/src/bootstrapper.cc

Lines 113 to 129 in 7d46437

	void SetupPromises(const FunctionCallbackInfo<Value>& args) {
	Environment* env = Environment::GetCurrent(args);
	Isolate* isolate = env->isolate();
	CHECK(args[0]->IsFunction());
	CHECK(args[1]->IsObject());
	Local<Object> constants = args[1].As<Object>();
	NODE_DEFINE_CONSTANT(constants, kPromiseRejectWithNoHandler);
	NODE_DEFINE_CONSTANT(constants, kPromiseHandlerAddedAfterReject);
	NODE_DEFINE_CONSTANT(constants, kPromiseResolveAfterResolved);
	NODE_DEFINE_CONSTANT(constants, kPromiseRejectAfterResolved);
	isolate->SetPromiseRejectCallback(PromiseRejectCallback);
	env->set_promise_handler_function(args[0].As<Function>());
	}