This is a new move. Black normally captures the knight as soon as it's unpinned.
1. c2c4  1... g8f6  2. b1c3  2... e7e5  3. g1f3  3... b8c6  4. d2d4 Carlsen likes the English Opening and plays it often, but the text move is a new weapon in his arsenal, as I haven't found any games of his with this move. 4... e5d4  5. f3d4  5... f8b4  6. g2g3  6... e8g8  7. f1g2  7... f8e8  8. e1g1 