Improve formatting of Rc and Arc source

Add some line breaks where they were missing between blocks.

Author: tgross35

library/alloc/src/rc.rs

@@ -656,6 +656,7 @@ impl<T> Rc<T> {
             )?))
         }
     }
+
     /// Constructs a new `Pin<Rc<T>>`. If `T` does not implement `Unpin`, then
     /// `value` will be pinned in memory and unable to be moved.
     #[inline]
@@ -678,6 +679,7 @@ impl<T, A: Allocator> Rc<T, A> {
     pub fn allocator(this: &Self) -> &A {
         &this.alloc
     }
+
     /// Constructs a new `Rc` in the provided allocator.
     ///
     /// # Examples

library/alloc/src/sync.rs

@@ -926,6 +926,7 @@ impl<T, A: Allocator> Arc<T, A> {
             ))
         }
     }
+
     /// Returns the inner value, if the `Arc` has exactly one strong reference.
     ///
     /// Otherwise, an [`Err`] is returned with the same `Arc` that was
@@ -3192,6 +3193,7 @@ impl<T: ?Sized + PartialOrd, A: Allocator> PartialOrd for Arc<T, A> {
         *(*self) >= *(*other)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized + Ord, A: Allocator> Ord for Arc<T, A> {
     /// Comparison for two `Arc`s.
@@ -3213,6 +3215,7 @@ impl<T: ?Sized + Ord, A: Allocator> Ord for Arc<T, A> {
         (**self).cmp(&**other)
     }
 }
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized + Eq, A: Allocator> Eq for Arc<T, A> {}