(Adds revised pricing)DUBAI, June 23 (Reuters) - Abu Dhabi&aposs Al Hilal Bank plans to raise $500 million from a capital-boosting Islamic bond issue, with pricing tightening ahead of completion on Tuesday due to investor demand, a document from lead arrangers said on Monday.Pricing for the transaction, which has a perpetual tenor but can be bought back by the lender after the fifth year, was revi