The ornamental design for a separable shower curtain, as shown and described.
FIG. 1 is a perspective view of a separable shower curtain showing my new design;
FIG. 2 is an exploded front view thereof;
FIG. 3 is an exploded back view thereof;
FIG. 4 is an exploded side view (opposite side view is mirror image) thereof;
FIG. 5 is a top view thereof;
FIG. 6 is a bottom view thereof; and,
FIG. 7 is an exploded perspective view of an in-use separable shower curtain.
In FIG. 7, the broken lines showing of environmental structure for purposes of illustrating the separable shower curtain in a condition of use. The broken lines and the structure they depict form no part of the claimed design.