By James Davey LONDON (Reuters) -Tesco, Britain’s biggest retailer, upgraded its profit outlook for the second time in four months as it reported a better-than-expected rise in underlying UK sales for the key Christmas trading period, buoyed by demand for fresh food. Shares in the supermarket group, which has a near 28% share of Britain’s grocery market, were up 1% early on Thursday, extending gains over the last year to 23% after the company also said it had “great momentum” going into 2024. CEO Ken Murphy told reporters he was “cautiously optimistic” about the health of the UK consumer, noti…