Docs: Fix links

Author: nseidle

docs/firmware_update.md

@@ -6,11 +6,11 @@ The RTK Devices run a variety of firmware. Please see the device specific pages
 
 ## RTK Torch
 
-* [Updating ESP32 Firmware](firmware_update_stm32.md)
+* [Updating ESP32 Firmware](firmware_update_esp32.md)
 * [Updating UM980 Firmware](firmware_update_um980.md)
 * [Updating STM32 Firmware](firmware_update_stm32.md)
 
 ## RTK EVK
 
-* [Updating ESP32 Firmware](firmware_update_stm32.md)
+* [Updating ESP32 Firmware](firmware_update_esp32.md)
 * [Updating u-blox Firmware](firmware_update_ublox.md)