PARIS, July 19 (Reuters) - Billionaire investor William Ackman’s Pershing Square Tontine Holdings has dropped a deal to buy 10% of Vivendi’s Universal Music Group (UMG), the label that is home to musicians such as Taylor Swift. “Our decision to seek an alternative initial business combination (‘IBC’) was driven by issues raised by the SEC with several elements of the proposed transaction – in particular, whether the structure of our IBC qualified under the NYSE rules,” Pershing said in a statement on Monday.