LONDON (Reuters) – Valentin Yumashev, the son-in-law of former Russian leader Boris Yeltsin who helped Vladimir Putin come to power, has quit his role as a Kremlin advisor, two people familiar with Yumashev’s thinking told Reuters. Yumashev was an unpaid advisor with limited influence on Putin’s decision-making, but his departure removes one of the last links inside Putin’s administration to Yeltsin’s rule, a period of liberal reforms and of Russian opening up towards the West. Putin ordered his armed forces to attack Ukraine on Feb. 24 in an invasion that Western governments say is an act of …