By Lars Mucklejohn City grandees are talking up a potential rebound for the beleaguered London Stock Exchange this year as fast fashion giant Shein and computer firm Raspberry Pi reportedly plot bumper listings in the capital. The two big-ticket listings would come as a much-needed boost for London’s struggling stock market, which has been hit by a dearth of IPOs, heavy investor outflows and an exodus of firms delisting or being taken private. The government and regulators are racing to implement a slew of capital market reforms to boost London’s attractiveness as a trading venue. “The pipelin…