The Concord City Council on Tuesday approved sweeping changes to its rental housing laws, including the rolling back of the city’s rent mediation program and new requirements surrounding fixed-term leases and relocation assistance. The changes are the culmination of a multi-year review of the city’s landlord-tenant policies. They also follow repeated efforts by Concord tenant advocacy groups to bring rent control and “just cause” eviction policies to the city — efforts the California Apartment Association continues to thwart.