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/reviung41/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/reviung41/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/reviung41/reviung41.overlay

@@ -27,7 +27,6 @@ RC(2,0) RC(2,1) RC(2,2) RC(2,3) RC(2,4) RC(2,5) RC(5,0) RC(5,1) RC(5,2) RC(5,3)
 
     kscan0: kscan_0 {
         compatible = "zmk,kscan-gpio-matrix";
-        label = "KSCAN";
         diode-direction = "col2row";
 
         col-gpios