The ornamental design for a vent grille, as shown and described.
FIG. 1 is a perspective view of a vent grille according to this invention;
FIG. 2 is a top view of the vent grille shown in FIG. 1;
FIG. 3 is a bottom view of the vent grille shown in FIG. 1;
FIG. 4 is a front view of the vent grille shown in FIG. 1;
FIG. 5 is a back view of the vent grille shown in FIG. 1;
FIG. 6 is a right side view of the vent grille shown in FIG. 1; and,
FIG. 7 is a left side view of the vent grille shown in FIG. 1.
The broken line showing of parts of the drawings is included for the purpose of illustrating use and environment and forms no part of the claimed design.