CAPE TOWN, South Africa — South Africa’s president promised Sunday to act on what he called concerns over illegal migration following a rise in anti-immigrant protests and sentiment in Africa’s most advanced economy, with other nations claiming their citizens have been targeted in xenophobic attacks. President Cyril Ramaphosa’s comments in a speech on national television dedicated to the issue were an acknowledgment of the tensions. Anti-migrant protest groups have said they’ve set a June 30