[libc++][doc] Removes a colon in a title.

NOKEYCHECK=True
GitOrigin-RevId: 8aa596584a3a1d77cedd1236d4cf17f002892218
diff --git a/docs/UsingLibcxx.rst b/docs/UsingLibcxx.rst
index f2bed0d..f69f999 100644
--- a/docs/UsingLibcxx.rst
+++ b/docs/UsingLibcxx.rst
@@ -298,8 +298,8 @@
   This macro is used to re-enable `set_unexpected`, `get_unexpected`, and
   `unexpected`.
 
-C++20 Specific Configuration Macros:
-------------------------------------
+C++20 Specific Configuration Macros
+-----------------------------------
 **_LIBCPP_DISABLE_NODISCARD_AFTER_CXX17**:
   This macro can be used to disable diagnostics emitted from functions marked
   ``[[nodiscard]]`` in dialects after C++17.  See :ref:`Extended Applications of [[nodiscard]] <nodiscard extension>`