Allow illegal_floating_point_literal_pattern. These will need to be updated at some point.

Discussion can be found on rust-lang/rust#41620.

src/test/ui/run-pass/union/union-pat-refutability.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 // run-pass
+#![allow(illegal_floating_point_literal_pattern)]
 
 #[repr(u32)]
 enum Tag { I, F }