The ornamental design for a armsleeve, as shown and described.
FIG. 1 is an alternate perspective view of an arm sleeve showing my new design;
FIG. 2 is a left side elevational view thereof;
FIG. 3 is a right side elevational view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a bottom plan view thereof;
FIG. 6 is a front elevational view thereof; and,
FIG. 7 is a rear elevational view thereof.
The indicia or broken lines shown on the figures are for illustrative purposes only and are hereby disclaimed as forming no part of Applicant's claimed invention.