Update codecov badge url (#1283)

Author: DakshitBabbar

README.md

@@ -1,5 +1,5 @@
 [![CMock Unit Tests](https://github.com/FreeRTOS/FreeRTOS-Kernel/actions/workflows/unit-tests.yml/badge.svg?branch=main&event=push)](https://github.com/FreeRTOS/FreeRTOS-Kernel/actions/workflows/unit-tests.yml?query=branch%3Amain+event%3Apush+workflow%3A%22CMock+Unit+Tests%22++)
-[![codecov](https://codecov.io/gh/FreeRTOS/FreeRTOS-Kernel/badge.svg?branch=main)](https://codecov.io/gh/FreeRTOS/FreeRTOS-Kernel)
+[![codecov](https://app.codecov.io/gh/FreeRTOS/FreeRTOS-Kernel/badge.svg?branch=main)](https://codecov.io/gh/FreeRTOS/FreeRTOS-Kernel)
 
 ## Getting started