The ornamental design for a pouring spout, as shown and described.
FIG. 1 is a perspective view showing a pouring spout embodying the design of the present invention, as attached in a first, storage position, to a bottle which is shown in phantom outline and does not form a portion of the present invention;
FIG. 2 is a perspective view showing the pouring spout embodying the design of the present invention, as attached in a second, use, position, to a bottle which is shown in phantom outline and does not form a portion of the present invention;
FIG. 3 is a perspective view of the pouring spout embodying the design of the present invention;
FIG. 4 is a top plan view of the pouring spout of FIG. 3;
FIG. 5 is a front elevation view of the pouring spout of FIG. 3; and,
FIG. 6 is a bottom plan view of the pouring spout of FIG. 3.