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/romac_plus/boards/nice_nano.overlay

@@ -25,7 +25,6 @@
 
     led_strip: ws2812@0 {
         compatible = "worldsemi,ws2812-spi";
-        label = "WS2812";
 
         /* SPI */
         reg = <0>; /* ignored, but necessary for SPI bindings */

app/boards/shields/romac_plus/boards/nice_nano_v2.overlay

@@ -25,7 +25,6 @@
 
     led_strip: ws2812@0 {
         compatible = "worldsemi,ws2812-spi";
-        label = "WS2812";
 
         /* SPI */
         reg = <0>; /* ignored, but necessary for SPI bindings */

app/boards/shields/romac_plus/romac_plus.dtsi

@@ -27,7 +27,6 @@ RC(3,0) RC(3,1) RC(3,2)
 
     kscan0: kscan {
         compatible = "zmk,kscan-gpio-matrix";
-        label = "KSCAN";
 
         diode-direction = "col2row";
         row-gpios
@@ -40,7 +39,6 @@ RC(3,0) RC(3,1) RC(3,2)
 
     left_encoder: encoder_left {
         compatible = "alps,ec11";
-        label = "LEFT_ENCODER";
         a-gpios = <&pro_micro 16 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
         b-gpios = <&pro_micro 14 (GPIO_ACTIVE_HIGH | GPIO_PULL_UP)>;
         steps = <80>;

app/boards/shields/romac_plus/romac_plus.overlay

@@ -13,7 +13,6 @@
 
     kscan0: kscan {
         compatible = "zmk,kscan-gpio-matrix";
-        label = "KSCAN";
 
         diode-direction = "col2row";