Revert "use correct cast function when doing `@floatCast` at comptime"

This reverts commit 2e1bdd0d14f490a80bbed3ee0e0479a908715d33.

Test failures
02619edf41Andrew Kelley committed on 7/10/2020, 6:24:21 AMparent2e1bdd0
2 files changedLine totals unavailable