Protein in mayonnaise...none?
It's just rounding. The Hellman's nutrition matches the USDA generic mayonnaise nutrition very closely for the single serving size (1 tbsp, 13.8g), but the USDA one also includes amounts per 100g. It's 0.96g protein per 100g, and when scaled down to the serving size that's only 0.13g and gets rounded to 0.