By Rhea Binoy (Reuters) -Twitter on Saturday updated its app in Apple’s App Store to begin charging $8 for sought-after blue check verification marks, in Elon Musk’s first major revision of the social media platform. The change comes a week after Musk took over the social media company in a $44 billion deal. The billionaire entrepreneur and CEO of electric car maker Tesla cut half the staff at Twitter and has vowed to start charging users more. In an update to Apple iOS devices, Twitter said those who “sign up now” for $7.99 a month can receive the blue checkmark next to their user names, “jus…