Get rid of unnecessary #![feature(core_float)].

Centril · web-flow · commit c2217b7fb7d0 · 2018-08-19T18:37:00.000+02:00
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
@@ -252,7 +252,6 @@
 #![feature(char_error_internals)]
 #![feature(compiler_builtins_lib)]
 #![feature(const_fn)]
-#![feature(core_float)]
 #![feature(const_int_ops)]
 #![feature(const_ip)]
 #![feature(convert_id)]
