The ornamental design for faucet stream straightener, as shown and described.
FIG. 1 is a top plan view of a faucet stream straightener in accordance my design;
FIG. 2 is a top, front perspective view thereof;
FIG. 3 is a bottom plan view thereof;
FIG. 4 is a bottom, rear perspective view thereof;
FIG. 5 is a front elevational view thereof, the rear elevational view being a mirror image thereof; and,
FIG. 6 is a left side elevational view thereof, with the right side elevational view being a mirror image thereof.
The stippled shading represents a contrast in appearance only and does not represent a particular color, material, texture, or finish. The broken lines represent portions of the faucet stream straightener that form no part of the claimed design.