po: update Italian translation

Reported-by: bovirus <https://gitlab.com/bovirus>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2451
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

po/it.po

@@ -65,7 +65,7 @@ msgid "Detach Tab"
 msgstr "_Sposta in una nuova finestra"
 
 msgid "Show Menubar"
-msgstr ""
+msgstr "Mostra _barra dei menu"
 
 msgid "_Machine"
 msgstr "_Macchina virtuale"