Update cdc_dfu_flash.rst

Author: jurstu

Diff for: docs/en/tutorials/cdc_dfu_flash.rst

@@ -66,7 +66,7 @@ Go to the Tools menu in the Arduino IDE and set the following options:
 
 * USB DFU On Boot -> Enabled
 
-Setp 3 - Flash
+Step 3 - Flash
 ^^^^^^^^^^^^^^
 
 Now you can upload your sketch to the device. After flashing, you need to manually reset the device.