[BoundsSafety][doc] Add a missing newline in C snippet

Author: pfusik

clang/docs/BoundsSafety.rst

@@ -959,7 +959,8 @@ that has the define.
    #if defined(__has_feature) && __has_feature(bounds_safety)
    #define __counted_by(T) __attribute__((__counted_by__(T)))
    // ... other bounds annotations
-   #else #define __counted_by(T) // defined as nothing
+   #else
+   #define __counted_by(T) // defined as nothing
    // ... other bounds annotations
    #endif
 
@@ -1003,4 +1004,4 @@ Try it out
 
 Your feedback on the programming model is valuable. You may want to follow the
 instruction in :doc:`BoundsSafetyAdoptionGuide` to play with ``-fbounds-safety``
-and please send your feedback to `Yeoul Na <mailto:[email protected]>`_.
+and please send your feedback to `Yeoul Na <mailto:[email protected]>`_.