The ornamental design for a mixer tap, as shown and described.
FIG. 1 is a perspective view of a mixer tap;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a left side elevation view thereof;
FIG. 7 is a right side elevation view thereof; and,
FIG. 8 is a magnified view of the handle portion bounded by the dashed-line rectangle in FIG. 3.
The dashed-line rectangle shown in FIG. 3 forms no part of the claimed design.
The broken line showing of the spout (FIGS. 2 and 5) and the handle (FIG. 8) is for the purpose of illustrating portions of the mixer tap and forms no part of the claimed design.