Fix "WARNING: Title underline too short." introduced by r254404.

Patch by Max Ostapenko. 

llvm-svn: 254413

Author: Yury Gribov

llvm/docs/LangRef.rst

@@ -9340,7 +9340,7 @@ See the description for :ref:`llvm.stacksave <int_stacksave>`.
 .. _int_get_dynamic_area_offset:
 
 '``llvm.get.dynamic.area.offset``' Intrinsic
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 Syntax:
 """""""