Fix bit-rotted reference to GetUserName() ...

it's GetUserNameFromId() now.

contrib/spi/insert_username.c

@@ -65,7 +65,7 @@ insert_username(PG_FUNCTION_ARGS)
 
 	/* create fields containing name */
 	newval = DirectFunctionCall1(textin,
-							  CStringGetDatum(GetUserName(GetUserId())));
+							  CStringGetDatum(GetUserNameFromId(GetUserId())));
 
 	/* construct new tuple */
 	rettuple = SPI_modifytuple(rel, rettuple, 1, &attnum, &newval, NULL);