You will need to go to tools, options, system options, Hole Wizard/Toolbox and click on configure..
In Welcome to Toolbox Setup click on option 1. Hole Wizard
In the left pane, expand the ISO standard, next expand Tapped Holes and select Tapped Hole.
Under Standard Properties select Thread Data
What you want to change is found under Thread Description column
After adding the spaces between the x, save and close
You may need to restart SolidWorks to see the changes
Existing Taps must be changed to a different size, then changed back to the original size to see the changes.