revert PR 7100 restoring the ability to read the buffer when no serial client is connected

the original issue if fixed in tinyusb

Author: Neradoc

shared-module/usb_cdc/Serial.c

@@ -19,9 +19,7 @@ size_t common_hal_usb_cdc_serial_read(usb_cdc_serial_obj_t *self, uint8_t *data,
     // Read up to len bytes immediately.
     // The number of bytes read will not be larger than what is already in the TinyUSB FIFO.
     uint32_t total_num_read = 0;
-    if (tud_cdc_n_connected(self->idx)) {
-        total_num_read = tud_cdc_n_read(self->idx, data, len);
-    }
+    total_num_read = tud_cdc_n_read(self->idx, data, len);
 
     if (wait_forever || wait_for_timeout) {
         // Continue filling the buffer past what we already read.
@@ -48,9 +46,7 @@ size_t common_hal_usb_cdc_serial_read(usb_cdc_serial_obj_t *self, uint8_t *data,
             data += num_read;
 
             // Try to read another batch of bytes.
-            if (tud_cdc_n_connected(self->idx)) {
-                num_read = tud_cdc_n_read(self->idx, data, len);
-            }
+            num_read = tud_cdc_n_read(self->idx, data, len);
             total_num_read += num_read;
         }
     }