BOSTON — Those in upper-income brackets will pay somewhat more in Social Security and medicare taxes in 1992.The cap on wages subject to the Social Security tax will rise $2,100 to $55,500 in 1992 from $53,400 in 1991. In the case of medicare, the maximum wage base will increase $5,200 to $130,200 from $125,000. Wages above these caps are not subject to the tax. This means the maximum Social Security tax, including medicare, an individual must pay will rise $205.60 to $5,328.90 in 1992. However, the tax rates - 6.2 percent for the old-age, survivors, and disabilities insurance, and 1.45 percent for medicare hospital insurance - will remain constant.