Update links in USBMIDI.md

Point links to development instead of the feature branch.

Author: Amanda Butler

docs/api/usb/USBMIDI.md

@@ -1,14 +1,14 @@
 ## USBMIDI
 
-<span class="images">![](https://os.mbed.com/docs/development/feature-hal-spec-usb-device-doxy/class_u_s_b_m_i_d_i.png)<span>USBMIDI class hierarchy</span></span>
+<span class="images">![](https://os.mbed.com/docs/mbed-os/development/mbed-os-api-doxy/class_u_s_b_m_i_d_i.png)<span>USBMIDI class hierarchy</span></span>
 
 You can use the USBMIDI interface to send and receive MIDI messages over USB using the standard USB-MIDI protocol.
 
 Examples of tasks you can perform using this library include sending MIDI messages to a computer (such as to record in a sequencer, or trigger a software synthesiser) and receiving messages from a computer (such as actuating things based on MIDI events).
 
 ### USBMIDI class reference
 
-[![View code](https://www.mbed.com/embed/?type=library)](http://os.mbed.com/docs/development/feature-hal-spec-usb-device-doxy/class_u_s_b_m_i_d_i.html)
+[![View code](https://www.mbed.com/embed/?type=library)](https://os.mbed.com/docs/mbed-os/development/mbed-os-api-doxy/class_u_s_b_m_i_d_i.html)
 
 The two examples below use a program called "Anvil Studio 32-bit" to play MIDI notes from an Mbed board through the host PC. You can play back the MIDI notes through headphones or speakers by following the steps below: