Update ArduinoCore-Linux/cores/arduino/libb64/cdecode.c

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: MitchBradley

ArduinoCore-Linux/cores/arduino/libb64/cdecode.c

@@ -94,9 +94,9 @@ int base64_decode_value(char value_in){
 }
 
 int base64_decode_block(const char* code_in, const int length_in, char* plaintext_out, base64_decodestate* state_in){
-  return base64_decode_block_signed((int8_t *) code_in, length_in, (int8_t *) plaintext_out, state_in);
+  return base64_decode_block_signed((const int8_t *) code_in, length_in, (int8_t *) plaintext_out, state_in);
 }
 
 int base64_decode_chars(const char* code_in, const int length_in, char* plaintext_out){
-  return base64_decode_chars_signed((int8_t *) code_in, length_in, (int8_t *) plaintext_out);
+  return base64_decode_chars_signed((const int8_t *) code_in, length_in, (int8_t *) plaintext_out);
 }