scripted-diff: get rid of remaining "command" terminology in protocol.{h,cpp}

-BEGIN VERIFY SCRIPT-
sed -i s/COMMAND_SIZE/MESSAGE_TYPE_SIZE/g $(git grep -l COMMAND_SIZE)
sed -i s/pszCommand/msg_type/g $(git grep -l pszCommand)
sed -i s/pchCommand/m_msg_type/g $(git grep -l pchCommand)
sed -i s/GetCommand/GetMessageType/g ./src/net.cpp ./src/protocol.cpp ./src/protocol.h ./src/test/fuzz/protocol.cpp
sed -i s/IsCommandValid/IsMessageTypeValid/g $(git grep -l IsCommandValid)
sed -i "s/command/message type/g" ./src/protocol.h ./src/protocol.cpp
-END VERIFY SCRIPT-

src/test/fuzz/protocol.cpp

@@ -20,7 +20,7 @@ FUZZ_TARGET(protocol)
         return;
     }
     try {
-        (void)inv->GetCommand();
+        (void)inv->GetMessageType();
     } catch (const std::out_of_range&) {
     }
     (void)inv->ToString();