Hello,
I do agree with JBW. This should be achieved through JS.
But if you do want to modify the source code, the class that you want to look into is src/Core/Grid/Definition/Factory/OrderGridDefinitionFactory.php - commenting out line 491 will remove the popup that's displayed on hover.
I tested the above with PS 8.2 - not really sure what PS version are you using, but it should work fine on 8 - assuming, of course, you do not have the grid code overridden.