The ornamental design for a solar-powered lamp, as shown and described.
FIG. 1 is a perspective view of a solar-powered lamp showing our new design, with its hinged support bracket in a closed position;
FIG. 2 is another perspective view thereof, with its hinged support bracket in an open position;
FIG. 3 is a rear elevational view thereof;
FIG. 4 is a front elevational view thereof;
FIG. 5 is a left side view elevational view thereof, with its hinged support bracket in a closed position;
FIG. 6 is right side elevational view thereof, with its hinged support bracket in a closed position;
FIG. 7 is a bottom plan view thereof, with its hinged support bracket in a closed position; and,
FIG. 8 is a top plan view thereof, with its hinged support bracket in a closed position.
The broken-line disclosure in the views is understood to represent portions of the article in which the claimed design is embodied, but which form no part of the claimed design.