Remove unused and incorrect Wrapping impl

This is used in the predictor and should be reversible but for floating
point the simply addition is not. It should instead be some variant of
byte casting but it hasn't been implemented yet.

src/decoder/mod.rs

@@ -237,18 +237,6 @@ impl Wrapping for u64 {
     }
 }
 
-impl Wrapping for f32 {
-    fn wrapping_add(&self, other: Self) -> Self {
-        self + other
-    }
-}
-
-impl Wrapping for f64 {
-    fn wrapping_add(&self, other: Self) -> Self {
-        self + other
-    }
-}
-
 fn rev_hpredict_nsamp<T>(image: &mut [T], size: (u32, u32), samples: usize) -> TiffResult<()>
 where
     T: Copy + Wrapping,