The ornamental design for a warm-up jacket, as shown and described.
FIG. 1 is a front elevational view of a warm-up jacket showing my new
design in use, the broken lines partially showing a human form in both
views being for illustrative purposes only and forming no part of the
claimed design; and,
FIG. 2 is a rear elevational view thereof.
The partial broken line showings of the human form in FIG. 1 and FIG. 2 are
for illustrative purposes only and form no part of the claimed design.