Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) says that this verse, namely "a ransom: the feeding of poor people", has been abrogated by "So whoever of you witnesses the month, let him fast it" [Surah al-Baqarah: 185].
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصيام / 7898