ZURICH (Reuters) -Credit Suisse Group AG’s credit rating has been downgraded to BBB from BBB+ by Standard & Poors, a blow for the Swiss bank which reported a first quarter loss and is facing increasing shareholder unrest following a string of scandals. Its outlook was changed to stable from negative, the rating agency said. Credit Suisse reported a first-quarter loss last month and launched a management overhaul after racking up billions in losses during 2021 from failed investments. Investors voiced their discontent by rejecting the board’s proposal to discharge management from liabilities fo…