Remove obsolete callback constructor code for @audioplayer, @audiorecorder (bug #64379) Remove ancient code for a calling form of @audioplayer, @audiorecorder constructor that is not supported by Matlab and has been commented out and unavailable in Octave for years. * audiodevinfo.cc (init_fn): Delete function. * audiodevinfo.cc (__recorder_audiorecorder__): Remove calling form with first argument a function from Texinfo focumentation. Remove input validation to check for function as first argument. Remove potential call to init_fn(). * audioplayer.m: Remove commented-out documentation for calling form with callback function. Remove input validation checking for function as first argument. Add FIXME note about incomplete input validation for this function. Remove commented-out BIST tests for this functionality. Add BIST test for existing input validation. * audiorecorder.m: Remove commented-out documentation for calling form with callback function. Remove input validation checking for function as first argument. Add FIXME note about lack of input validation for this function. Remove commented-out BIST tests for this functionality. Add BIST tests for existing input validation.