[Documentation] Minor adjustment ESP32 > ESP32C3

[nicolasdb]

I feel important to specify the exact model we use, while esp32 and esp32C3 are kinda similar, the C3 is the first ESP32 chip to use the RISC-V architecture and thus require a specific micropython firmware which will not work with others boards.

But the code should work with any flavor of esp32... or micropython platforms, I guess. (not tested)

I'll create a branch to update the documentation, asap.