Remove remaining style classes references

[asheemmamoowala]

Carried forward from #11477(comment).

Documentation for style classes still exists in the node bindings in the Readme.

Cod for parsing style classes also lingers in:

mapbox-gl-native/platform/node/src/node_map.cpp

Lines 314 to 321 in 553efa3

	if (Nan::Has(obj, Nan::New("classes").ToLocalChecked()).FromJust()) {
	auto classes = Nan::To<v8::Object>(Nan::Get(obj, Nan::New("classes").ToLocalChecked()).ToLocalChecked()).ToLocalChecked().As<v8::Array>();
	const int length = classes->Length();
	options.classes.reserve(length);
	for (int i = 0; i < length; i++) {
	options.classes.emplace_back(std::string { *Nan::Utf8String(Nan::To<v8::String>(Nan::Get(classes, i).ToLocalChecked()).ToLocalChecked()) });
	}
	}

Both of these references should be removed. Style classes were removed from the rest of the code base in #8953.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[asheemmamoowala]

This is still valuable code & doc cleanup that should be done

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[stale]

This issue has been automatically detected as stale because it has not had recent activity and will be archived. Thank you for your contributions.

[alexshalamov]

/cc @springmeyer

[1rayanharoon]

Hey, I am a beginner at open source. Can you please tell/guide me on what contribution I could make here?