[netdata] allow Publisher to be build with service only (#7132)

This commit adds missing `#if` check in `network_data_publisher.cpp`
to ensure it can be built when `CONFIG_BORDER_ROUTER_ENABLE` is
disabled (i.e., with `CONFIG_TMF_NETDATA_SERVICE_ENABLE` only).

src/core/thread/network_data_publisher.cpp

@@ -836,6 +836,8 @@ Publisher::DnsSrpServiceEntry::Info::Info(Type aType, uint16_t aPortOrSeqNumber,
 
 #endif // OPENTHREAD_CONFIG_TMF_NETDATA_SERVICE_ENABLE
 
+#if OPENTHREAD_CONFIG_BORDER_ROUTER_ENABLE
+
 //---------------------------------------------------------------------------------------------------------------------
 // Publisher::PrefixEntry
 
@@ -1089,6 +1091,8 @@ exit:
     return;
 }
 
+#endif // OPENTHREAD_CONFIG_BORDER_ROUTER_ENABLE
+
 } // namespace NetworkData
 } // namespace ot