The ornamental design for a dispenser, as shown and described.
1.1 : Perspective
1.2 : Front
1.3 : Left
1.4 : Top
1.5 : Perspective
1.6 : Bottom
1.7 : Back
2.1 : Perspective
2.2 : Front
2.3 : Left
2.4 : Top
2.5 : Perspective
2.6 : Back
2.7 : Bottom
The right views have been omitted because they are a mirror image of the left views shown in 1.3 and 2.3. The broken lines showing a sink in views 1.1 and 2.1 illustrates environment and forms not part of the claimed design. All other broken lines show portions of the dispenser that form not part of the claimed design.