Nicki Minajisn’t taking her foot off Megan Thee Stallion’s neck and is preparing to “drown” her ex-pal, RadarOnline.com has learned. The feud reached a head last week, beginning when Minaj dropped Big Foot, mocking Megan about being shot by Tory Lanez after the latter’s diss track Hiss, which seemingly referenced Nicki’s registered sex offender husband. Minaj unloaded on Megan, even dragging the rapper’s dead mother into the conversation. Her Barbz fans went as far as doxxing the cemetery where Megan’s mom is buried — but even that won’t stop Nicki, who’s unapologetic and reportedly gearing up…