Replace wait() with ThisThread::sleep_for()

As the wait() API has been deprecated, let's use what the deprecation
note proposed instead.

wait() used floats as input parameter (1 = 1 second), the sleep_for
uses milliseconds.

Ref; https://os.mbed.com/docs/mbed-os/v5.15/mbed-os-api-doxy/namespacertos_1_1_this_thread.html

Author: Janne Kiiskila

main.cpp

@@ -229,7 +229,7 @@ int main(void)
         } else if (in_char == 'r') {
             (void) fcc_storage_delete(); // When 'r' is pressed, erase storage and reboot the board.
             printf("Storage erased, rebooting the device.\n\n");
-            wait(1);
+            ThisThread::sleep_for(1*1000);
             NVIC_SystemReset();
         } else if (in_char > 0 && in_char != 0x03) { // Ctrl+C is 0x03 in Mbed OS and Linux returns negative number
             value_increment(); // Simulate button press