The ornamental design for a pressureregulator, as shown and described.
FIG. 1 shows a front view of a pressure regulator showing my new design;
FIG. 2 shows a rear view thereof;
FIG. 3 shows a right side view thereof;
FIG. 4 shows a left side view thereof;
FIG. 5 shows a top view thereof;
FIG. 6 shows a bottom view thereof;
FIG. 7 shows a top, front and left side perspective view thereof; and,
FIG. 8 shows a bottom, rear and right side perspective view thereof.
The broken lines in the drawings are included for the purpose of illustrating portions of the pressure regulator and form no part of the claimed design.