Vinegar is slightly acidic due to the presence of acetic acid in it.
Sodium chloride is common salt. Sodium chloride is a salt of strong acid, hydrogen chloride and strong base, sodium hydroxide which is neutral in nature and has a of .
Being neutral in nature common salt will not make vinegar more acidic or more basic as will not cause any change in the of vinegar.
So, adding salt to vinegar does not make it more acidic.