BOSTON — A former Boston City Hall official who admitted accepting a bribe was sentenced in federal court Friday to just over three years in prison and one year of supervised release. John Lynch, who pleaded guilty in September to one count of bribery and one count of filing a false federal tax return, was also ordered to pay restitution of $14,400 and forfeit $50,000. Prosecutors had recommended a four-year sentence. Prosecutors said the 66-year-old former assistant director in the Boston Planning and Development Agency, accepted $50,000 in bribes from a developer trying to get a key city approval. They said Lynch used his influence to convince a Zoning Board of Appeals member to vote in favor of the developer’s request. Prosecutors highlighted a photo they say shows Lynch accepting a bribe. “Mr.