LONDON (Reuters) -Shares in Martin Sorrell’s S4 Capital plunged by 35% on Wednesday after auditors PwC said they were unable to complete the work needed for the digital advertising group to release its 2021 results on Thursday. S4 said in a statement to the stock exchange that it had been informed at 1330 GMT by PwC that the auditors were “unable to complete the work necessary” and that the results would be published as soon as PwC completed its work. “The company believes that the results for 2021 remain within the range of market expectations and continued to trade strongly in the first two …