refactor(nibble): enable oled in dts/overlay by default

app/boards/shields/nibble/README.md

@@ -28,10 +28,4 @@ If using an OLED screen, you'll need to change the following in your local nibbl
 CONFIG_ZMK_DISPLAY=y
 ```
 
-You'll also need to add the following to your keymap to ensure the OLED device is activated by the firmware.
-
-```
-&pro_micro_i2c {
-	status = "okay";
-}
 ```

app/boards/shields/nibble/nibble.overlay

@@ -56,7 +56,7 @@ RC(4,0) RC(4,1) RC(4,2) RC(4,3)                 RC(4,6)                 RC(4,9)
 };
 
 &pro_micro_i2c {
-	status = "disabled";
+	status = "okay";
 
 	oled: ssd1306@3c {
 		compatible = "solomon,ssd1306fb";