The ornamental design for a flexibleseal, as shown and described.
FIG. 1 is a front perspective view of a flexible seal showing my new design;
FIG. 2 is a rear perspective view thereof;
FIG. 3 is another front perspective view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof; and,
FIG. 6 is a side elevation view thereof.
The flexible seal is shown with a symbolic break in its length. The appearance of any portion of the flexible seal between the break lines forms no part of the claimed design.