A neutralization reaction is a reaction between an acid and a base. The typical reaction scheme is acid + base → water + salt. Vinegar is a solution of water and acetic acid (CH3COOH). Milk is an emulsion consisting of water, sugar, fats, oils and proteins. Normally water and fats or oils would not mix well, but when they are combined the combination is an emulsion. You can create an emulsion when mixing water and olive oil in the kitchen to make salad dressing. Milk has a close to neutral pH or is slightly acidic. This means that a neutralization reaction is not occurring between vinegar and milk, because there is no base present.
Instead what is happening is denaturation. Proteins are folded in a very specific shape using weak bonds like hydrogen bonds. When they are exposed to conditions that are substantially outside their normal environment, proteins unfold often in an irreversible manner. When you cook eggs, you denature the proteins in the yolks by adding heat. Changing the pH by adding an acid like acetic acid is another way to denature proteins. The main protein in milk is casein. This protein is denatured when vinegar is added to milk. This denaturing curdles the milk causing clumps of casein. So, the reaction between vinegar and milk is a denaturing reaction.