Update sycl_kernel_entry_point attribute documentation to include the non-deduced void return type requirement.

Author: tahonermann

clang/include/clang/Basic/AttrDocs.td

@@ -475,7 +475,7 @@ not first appear on a declaration that follows a definition of the function.
 The attribute only appertains to functions and only those that meet the
 following requirements.
 
-* Has a ``void`` return type.
+* Has a non-deduced ``void`` return type.
 * Is not a non-static member function, constructor, or destructor.
 * Is not a C variadic function.
 * Is not a coroutine.