Remove obsolete entry from the Doxygen configuration files.

Bootloaders/CDC/Doxygen.conf

Bootloaders/DFU/Doxygen.conf

Demos/Device/ClassDriver/AudioInput/Doxygen.conf

Demos/Device/ClassDriver/AudioOutput/Doxygen.conf

Demos/Device/ClassDriver/DualVirtualSerial/Doxygen.conf

Demos/Device/ClassDriver/GenericHID/Doxygen.conf

Demos/Device/ClassDriver/Joystick/Doxygen.conf

Demos/Device/ClassDriver/Keyboard/Doxygen.conf

Demos/Device/ClassDriver/KeyboardMouse/Doxygen.conf

Demos/Device/ClassDriver/MIDI/Doxygen.conf

Demos/Device/ClassDriver/MassStorage/Doxygen.conf

Demos/Device/ClassDriver/MassStorageKeyboard/Doxygen.conf

Demos/Device/ClassDriver/Mouse/Doxygen.conf

Demos/Device/ClassDriver/RNDISEthernet/Doxygen.conf

Demos/Device/ClassDriver/VirtualSerial/Doxygen.conf

Demos/Device/ClassDriver/VirtualSerialMouse/Doxygen.conf

Demos/Device/LowLevel/AudioInput/Doxygen.conf

Demos/Device/LowLevel/AudioOutput/Doxygen.conf

Demos/Device/LowLevel/DualVirtualSerial/Doxygen.conf

Demos/Device/LowLevel/GenericHID/Doxygen.conf