By Idrees Ali and Jonathan Landay WASHINGTON (Reuters) – The CIA drone strike that killed Al Qaeda leader Ayman al-Zawahiri delivered a long-sought win for U.S. President Joe Biden’s counter-terrorism strategy, officials and experts said on Tuesday, but also sharpened concerns about militants’ presence in Afghanistan. As the last U.S. troops and intelligence officers left Afghanistan last August after 20 years of war, Biden shifted to an “over-the-horizon” strategy of relying on drones and spy planes to track and hit al Qaeda and Islamic State militants inside the country. The CIA strike on Su…