Syrian opposition forces on Saturday made a new bid to revive their decade-old campaign against President Bashar al-Assad at talks in Qatar, where a senior leader said they had to “correct” past mistakes. The political groups, now mainly based abroad, have seen their influence wane in recent years as Iran and Russia steadfastly supported the Syrian president after he launched a deadly crackdown on protesters in 2011 that quickly descended into civil war. Riad Hijab, who defected to the opposition when he was Assad’s prime minister in 2012, told the opening of the two-day meeting that events in…