refactor: Remove unimportant labels

Removed "label" properties which no longer have any function.

Labels are still used as layer names and as identifiers for sending
behaviors between sides of a split keyboard, so those have been left
alone for now.

app/boards/shields/iris/iris.dtsi

@@ -32,7 +32,6 @@ RC(3,0) RC(3,1) RC(3,2) RC(3,3) RC(3,4) RC(3,5) RC(4,2) RC(4,9) RC(3,6) RC(3,7)
 
     kscan0: kscan {
         compatible = "zmk,kscan-gpio-matrix";
-        label = "KSCAN";
 
         diode-direction = "col2row";
         row-gpios