Texas Gov. Greg Abbott fired off a blistering letter threatening to yank state funding if one of his cities doesn’t shut down an “Muslim-only” bash hosted by an Islamic group at a taxpayer-funded water park. The Republican warned Grand Prairie Mayor Ron Jensen Wednesday that the state will pull back $530,000 in public safety grants if he doesn’t pull the plug on the upcoming Eid event at Epic Indoor Park, initially advertised as “exclusively reserved for Muslims,” according to a threatening letter obtained by The Post. The third-annual DFW Epic Eid also requires modest swimwear and was initially closed to the public. Texas Gov. Greg Abbott warned Grand Prairie Mayor Scott Jensen the state will yank $530,000 in grants if he doesn’t pull the plug on the annual Eid event. Getty Images Abbott blasted the June 1 event – held at the city-owned indoor park for the past two years – as discriminatory and a constitutional violation, and gave Jensen, who is politically unaffiliated, until Monday to call it off.…