fix: Replace the README reference to ESP32-H4 with reference to ESP32-H2

As the chip was renamed for release we don't need to refer to the old name.

README.md

@@ -19,7 +19,7 @@ Supported **target** microcontrollers:
 - ESP32-S3
 - ESP32-C3
 - ESP32-C2
-- ESP32-H4 (Beta1 and Beta2)
+- ESP32-H2
 
 ## Supporting new host target