By Bhanvi Satija and Yadarisa Shabong LONDON (Reuters) -GSK raised its 2025 sales and earnings forecasts on Wednesday as its speciality HIV and cancer medicines posted double digit growth, lifting the British drugmaker's shares to their highest level since mid-2024. Although GSK saw a sharp slide in U.S. sales of its shingles vaccine Shingrix, its shares added almost 4% to the gains of around 25% they have notched up so far this year. GSK's improved outlook comes as CEO Emma Walmsley prepares to hand ov ...