Copy the agency.xml to the custom folder and make edits to that one. Any file in the custom folder will override the default file in the parent folder. You don't need to change those values, just delete those 4 lines entirely. The police1,2 & 3 values are already there above the lines you circled.
edit: you don't need openiv to change these. just go straight to the lspdfr folder in your main GTA V directory.
edit2: also note that those cars are listed throughout the agency.xml file in other places as they are assigned to different agencies. You'll need to edit each agency to make sure they don't spawn in other places like the sheriffs dept.