I claim the ornamental design for a connecting device, as shown and described herein.
FIG. 1 is a top perspective view of a connecting device showing my new design;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left-side view thereof;
FIG. 5 is a right-side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof;
FIG. 8 is a top perspective view thereof, in an alternate position; and,
FIG. 9 is a top perspective view thereof, in another alternate position.
The even-broken line in FIG. 4 drawing view and the dash-dot-dot line in FIGS. 8 and 9 drawing views are included for the purpose of illustrating environment only and forms no part of the claimed design.