pico: remove printfs in PROG handling

The tools assume that any output during this command is an error

Author: Daft-Freak

32blit-pico/blit_launch.cpp

@@ -467,8 +467,6 @@ bool BlitWriter::prepare_write(const uint8_t *buf) {
   }
 #endif
 
-  printf("PROG: flash off %lu\n", flash_offset);
-
   disable_user_code();
 
   // erase flash

32blit-pico/usb.cpp

@@ -75,7 +75,6 @@ class CDCProgCommand final : public CDCCommand {
 
           // end of string
           if(*buf_ptr == 0) {
-            printf("PROG: file %s\n", buf.get_data());
             parse_state = ParseState::Length;
             buf.reset();
             continue;
@@ -98,7 +97,6 @@ class CDCProgCommand final : public CDCCommand {
           // end of string
           if(*buf_ptr == 0) {
             auto file_len = strtoul((const char *)buf.get_data(), nullptr, 10);
-            printf("PROG: len %lu\n", file_len);
             parse_state = ParseState::Data;
             buf.reset();