Fix formatting

Author: vogelsgesang

clang/docs/DebuggingCoroutines.rst

@@ -360,7 +360,7 @@ type of a task is a template argument. For simplicity's sake, we hard-coded the
 ``int`` type in this example.
 
 Stack traces of in-flight coroutines
------------------------------------
+------------------------------------
 
 Let's assume you have the following program and set a breakpoint inside the
 ``write_output`` function. There are multiple call paths through which this