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/arm/nice_nano/nice_nano.dtsi

@@ -23,7 +23,6 @@
         compatible = "gpio-leds";
         blue_led: led_0 {
             gpios = <&gpio0 15 GPIO_ACTIVE_HIGH>;
-            label = "Blue LED";
         };
     };
 };
@@ -63,7 +62,6 @@
     status = "okay";
     cdc_acm_uart: cdc_acm_uart {
         compatible = "zephyr,cdc-acm-uart";
-        label = "CDC_ACM_0";
     };
 };
 
@@ -79,11 +77,9 @@
         #size-cells = <1>;
 
         sd_partition: partition@0 {
-            label = "softdevice";
             reg = <0x00000000 0x00026000>;
         };
         code_partition: partition@26000 {
-            label = "code_partition";
             reg = <0x00026000 0x000c6000>;
         };
 
@@ -97,12 +93,10 @@
          * if enabled.
          */
         storage_partition: partition@ec000 {
-            label = "storage";
             reg = <0x000ec000 0x00008000>;
         };
 
         boot_partition: partition@f4000 {
-            label = "adafruit_boot";
             reg = <0x000f4000 0x0000c000>;
         };
     };