The ornamental design for a valvemanifold, as shown and described.
FIG. 1 is a perspective view of a valve manifold showing my new design;
FIG. 2 is a bottom view thereof;
FIG. 3 is a front view thereof;
FIG. 4 is a rear view thereof;
FIG. 5 is a first side view thereof, where a second side view is the same and is thus omitted; and,
FIG. 6 is a top view thereof.
The broken (dashed) lines shown in the figures are included for the purpose of illustrating portions of the valve manifold and form no part of the claimed design.