buddy: Add title to MMU error

This is a generic error that happens in Load/Unload with MMU. There is
large number of errors that can happen during the MMU Loading/Unloading
so we use a generic title here.

BFW-5773

yaml/buddy-error-codes.yaml

@@ -921,7 +921,7 @@ Errors:
 
   - code: "XX815"
     printers: [MK4, MK3.5]
-    title: ""
+    title: "MMU Error" # This is a generic error for any MMU error, so we use generic title, until we send mmu errors directly
     text: "Waiting for user input"
     id: "MMU_LOAD_UNLOAD_ERROR"
     type: "CONNECT"