MILANO (Reuters) – Two investors in Generali said on Tuesday they had dissolved a pact they had struck last year to challenge the Italian insurer’s top shareholder Mediobanca over the renewal of the board. Delfin, the holding of the Italian billionaire Leonardo del Vecchio, and Fondazione CRT said they ended the pact as of March 27 since the purposes for which they signed it have ceased to exist. Europe’s third-largest insurer is at the centre of a shareholder battle that has cast doubt on the reappointment of CEO Philippe Donnet, whose term ends in April. With the backing of Mediobanca, the i…