The ornamental design for a cooking pan, as shown and described.
1. Cooking pan
1.1: Perspective
1.2: Front
1.3: Left
1.4: Top
1.5: Bottom
1.6: Cross sectional
1.7: Cross sectional
The broken lines form no part of the claimed design; the rear view is omitted as it is identical with the front view; the right side view is omitted as it is identical with the left side view; 1.6is a cross sectional view taken along the line 1.6-1.6in 1.4; and 1.7is a cross sectional view taken along the line 1.7-1.7in 1.4.