CLEVELAND — The Kansas City Royals were shut out for the sixth time this season in a 4-0 loss to the Cleveland Guardians in the finale of a three-game series Wednesday at Progressive Field. The Royals’ losing slide extended to four consecutive games as they head into a day off on Thursday. The Royals (16-33) finished their three-city road trip, which included a two-game interleague set in Arizona, 2-7. Left fielder Andrew Benintendi collected three of the team’s seven hits on a day when he went 3 for 4. Carlos Santana (2 for 4) also had two hits. Royals starting pitcher Brad Keller allowed fou…