fix(macOS): Don't include iOS pull-to-refresh control (#1636)
* Update RNCWebView.h
Limit methods relating to pull to refresh to only iOS
* Update RNCWebView.m
Block methods relating to pull to refresh when the target is macOS as macOS does not have the UIRefreshControl
Co-authored-by: Eloy Durán <eloy.de.enige@gmail.com>