KUALA LUMPUR, June 26 (Reuters) - The Malaysian state of Sarawak on Borneo island will issue a 1.5 billion ringgit ($466.27 million) Islamic bond for funds to develop the sewerage system in its capital, said credit agency RAM Ratings on Thursday. The sukuk murabaha will be issued by Aquasar Capital, an indirect unit of Sarawak state. RAM rated the programme AAA or &aposstable&apos b