Because flutter_launcher_icons >=0.4.0 <0.6.1 depends on dart_config >=0.3.0+1 which requires SDK version <2.0.0, flutter_launcher_icons >=0.4.0 <0.6.1 is forbidden.
So, because two_zero_four_eight depends on flutter_launcher_icons ^0.5.2, version solving failed.
Because flutter_launcher_icons >=0.4.0 <0.6.1 depends on dart_config >=0.3.0+1 which requires SDK version <2.0.0, flutter_launcher_icons >=0.4.0 <0.6.1 is forbidden.
So, because two_zero_four_eight depends on flutter_launcher_icons ^0.5.2, version solving failed.