refactor: remove unnecessary casting (#552)

src/decoder/flac.rs

@@ -102,7 +102,7 @@ where
                     Ordering::Equal => raw_val as i16,
                     Ordering::Greater => (raw_val >> (self.bits_per_sample - 16)) as i16,
                 };
-                return Some(real_val as i16);
+                return Some(real_val);
             }
 
             // Load the next block.

src/source/skip.rs

@@ -48,7 +48,7 @@ where
             return;
         }
 
-        skip_samples(input, frame_len as usize);
+        skip_samples(input, frame_len);
 
         duration -= Duration::from_nanos((frame_len * ns_per_sample as usize) as u64);
     }