PFW-831 Add single buzzer beep when an MMU error screen is shown for the first time

If the user has the sound settings set to 'Silent' then this beep should be silent

Change in memory:
Flash: +4 bytes
SRAM: 0 bytes

Firmware/mmu2.cpp

@@ -911,6 +911,9 @@ void MMU2::ReportError(ErrorCode ec, ErrorSource res) {
         // or if 'Retry' operation is not available
         // raise the MMU error sceen and wait for user input
         ReportErrorHook((CommandInProgress)logic.CommandInProgress(), (uint16_t)ec, uint8_t(lastErrorSource));
+
+        // Beep when error screen is shown for the first time
+        MakeSound(Prompt);
     }
 
     static_assert(mmu2Magic[0] == 'M'