review: Inline attribute to body passthrough

continuing this theme of inlining, we inline the passthrough methods on
`Body` as well.

Signed-off-by: katelyn martin <[email protected]>

Author: cratelyn

linkerd/http/prom/src/body_data/body.rs

@@ -63,17 +63,20 @@ where
         Poll::Ready(data)
     }
 
+    #[inline]
     fn poll_trailers(
         self: Pin<&mut Self>,
         cx: &mut Context<'_>,
     ) -> Poll<Result<Option<HeaderMap>, Self::Error>> {
         self.project().inner.poll_trailers(cx)
     }
 
+    #[inline]
     fn is_end_stream(&self) -> bool {
         self.inner.is_end_stream()
     }
 
+    #[inline]
     fn size_hint(&self) -> SizeHint {
         self.inner.size_hint()
     }