WASHINGTON — Immigration and Customs Enforcement deputy director Madison Sheahan is resigning to run for Congress as a Republican in an Ohio district that’s been a Democratic stronghold since 1983, The Post can confirm. Sheahan launched her campaign challenging Rep. Marcy Kaptur (D-Ohio) on Thursday with a video announcement touting her service as an ICE official and work on her family’s horse farm. Ohio’s 9th District, which stretches across the northwestern corner of the Buckeye State and