What is claimed the ornamental design for a module tray system, as shown and described.
FIG. 1 is a front perspective view of a tray design of a module tray system design;
FIG. 2 is a top view of the tray design of the module tray system design;
FIG. 3 is a bottom view of the tray design of the module tray system design;
FIG. 4 is a front view of the tray design of the module tray system design; and,
FIG. 5 is a right side view of the tray design of the module tray system design.
The phantom lines showing indicia on the front of the module tray system are included for the purpose of illustrating portions of the module tray system and form no part of the claimed design.