The city’s unemployment rate crept downward in February by a tenth of a percentage point, to 6.6 percent, from 6.7 percent in January. The city’s jobless rate was higher a year ago at this time: 7.3 percent. Local unemployment rates are not adjusted for seasonal changes in the economy. So a year-over-year number is a more accurate snapshot of the local jobs market. The Massachusetts Executive Office of Labor and Workforce Development released updated figures Wednesday.