rustc_abi: remove Primitive::{is_float,is_int}

there were fixmes for this already

i am about to remove is_ptr (since callers need to properly distinguish
between pointers in different address spaces), so might as well do this
at the same time

compiler/rustc_abi/src/lib.rs

@@ -887,18 +887,6 @@ impl Primitive {
         }
     }
 
-    // FIXME(eddyb) remove, it's trivial thanks to `matches!`.
-    #[inline]
-    pub fn is_float(self) -> bool {
-        matches!(self, F32 | F64)
-    }
-
-    // FIXME(eddyb) remove, it's completely unused.
-    #[inline]
-    pub fn is_int(self) -> bool {
-        matches!(self, Int(..))
-    }
-
     #[inline]
     pub fn is_ptr(self) -> bool {
         matches!(self, Pointer)