MidiSettingsView: renamed box label

Renamed box label from "SoundFont" to "Available SoundFonts", hopefully
improves the user experience by making it clearer that this is a list
of the available soundfonts.

src/preferences/media/MidiSettingsView.cpp

@@ -37,7 +37,7 @@ MidiSettingsView::MidiSettingsView()
 	SettingsView()
 {
 	BBox* defaultsBox = new BBox("SoundFont");
-	defaultsBox->SetLabel(B_TRANSLATE("SoundFont"));
+	defaultsBox->SetLabel(B_TRANSLATE("Available SoundFonts"));
 	BGridView* defaultsGridView = new BGridView();
 
 	fListView = new BListView(B_SINGLE_SELECTION_LIST);