Update getting started links

UNO R3, Mega2560, and UNO mini le were all broken. This updates links.

Author: jacobhylen

content/hardware/02.hero/boards/mega-2560/product.md

@@ -1,7 +1,7 @@
 ---
 title: Mega 2560 Rev3
 url_shop: https://store.arduino.cc/arduino-mega-2560-rev3
-url_guide: https://www.arduino.cc/en/Guide/ArduinoMega2560
+url_guide: /software/ide-v1/tutorials/getting-started/cores/arduino-avr
 core: arduino:avr
 productCode: '002'
 certifications: [CE, FCC, UKCA]

content/hardware/02.hero/boards/uno-mini-le/product.md

@@ -1,7 +1,7 @@
 ---
 title: UNO Mini Limited Edition
 url_shop: https://store.arduino.cc/products/uno-mini-le
-url_guide: /tutorials/uno-mini/uno-mini-guide
+url_guide: /tutorials/uno-mini-le/uno-mini-le-guide
 core: arduino:avr
 productCode: '117'
 certifications: [CE, UKCA, FCC, RCM]

content/hardware/02.hero/boards/uno-rev3/product.md

@@ -1,7 +1,7 @@
 ---
 title: UNO R3
 url_shop: https://store.arduino.cc/arduino-uno-rev3
-url_guide: https://www.arduino.cc/en/Guide/ArduinoUno
+url_guide: /software/ide-v1/tutorials/getting-started/cores/arduino-avr
 core: arduino:avr
 certifications: [CE, FCC, GB4943, IC, RCM, REACH, RoHS, UKCA, WEEE]
 productCode: '001'