[libc] [nfc] Fix heading underline.

Differential Revision: https://reviews.llvm.org/D140825

diff --git a/libc/docs/source_tree_layout.rst b/libc/docs/source_tree_layout.rst
index cd328e7..3f7efd4 100644 (file)
--- a/libc/docs/source_tree_layout.rst
+++ b/libc/docs/source_tree_layout.rst
@@ -59,7 +59,7 @@ This directory contains a ``CMakeLists.txt`` file listing the targets for the
 public libraries ``libc.a``, ``libm.a`` etc.
 
 The ``startup`` directory
-------------------------
+-------------------------
 
 This directory contains the implementations of the application startup objects
 like ``crt1.o`` etc.