Use snprintf instead of u32_to_str

src/utils.h

@@ -28,9 +28,6 @@ void convertUint256BE(uint8_t* data, uint32_t length, uint256_t* target);
 
 int local_strchr(char* string, char ch);
 
-// `itoa` for uint32_t.
-void u32_to_str(char* dest, uint8_t dest_size, uint32_t in);
-
 // Converts a list of bytes (in BE) of length `size` to a uint32_t. `strict` will make the function
 // throw if the size is > 4.
 uint32_t u32_from_BE(uint8_t* in, uint8_t size, bool strict);