The new Apple Watch Series 4 will be getting its promised ECG feature as part of the upcoming watchOS 5.1.2 update, according to documents obtained by MacRumors. While the version of watchOS 5.1.2 that is currently in developer beta testing has not shown any indications of the ECG feature as of yet, internal Apple Store training documents have revealed that an ECG app will be included with the final public release of watchOS 5.1.2. As promised, the…