Doc: fixups for GUI helptexts wrt MT-32 rom scan_path

[giantclambake]

...just FTR I believe the mt32-roms dir should exist as it does now ~ an MT-32 is not an Amiga specific device, and it's roms certainly aren't kickstarts..grin... but searching rom_path as well makes sense.... anyhoo....

...for src/osdep/gui/PanelPaths.cpp

@ line 785 replace para with;

        helptext.emplace_back("- System ROMs: The Amiga Kickstart files are by default located under 'kickstarts'.");
        helptext.emplace_back("  After changing the location of the Kickstart ROMs, or adding any additional ROMs, ");
        helptext.emplace_back("  click on the \"Rescan\" button to refresh the list of the available ROMs. Please");
        helptext.emplace_back("  note that MT-32 ROM files may also reside here, or in a \"mt32-roms\" directory");
        helptext.emplace_back("  at this location, if you wish to use the MT-32 MIDI emulation feature in Amiberry.");

...for src/osdep/gui/PanelIOPorts.cpp

@ line 450 replace para with;

        helptext.emplace_back("MIDI Out/In: Amiberry uses the PortMidi library to send and receive MIDI messages,");
        helptext.emplace_back("         so if you have any MIDI devices connected, you can select them here. You");
        helptext.emplace_back("         can also emulate a Roland MT-32 MIDI device using Amiberry, if you have");
        helptext.emplace_back("         the required MT-32 ROM files installed. Please note that the path for ");
        helptext.emplace_back("         these ROM files must be in your System ROMs: directory as set in the ");
        helptext.emplace_back("         \"Paths\" panel, or inside a \"mt32-roms\" directory under that location.");
        helptext.emplace_back(" ");
        helptext.emplace_back("         If the required MT-32 ROMs are detected by Amiberry, you can then select"); 
        helptext.emplace_back("         the emulated MT-32 device, using the MIDI \"Out:\" dropdown options. This");
        helptext.emplace_back("         allows you to use any Amiga software that makes use of it (several Sierra"); 
        helptext.emplace_back("         games for example). The audio output here is mixed with Paula's output.");

TIA