doc-rst: Add missing newline at end of file

"git diff" says:

    \ No newline at end of file

after modifying the file.
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NJonathan Corbet <corbet@lwn.net>

Documentation/docutils.conf

@@ -4,4 +4,4 @@
 # http://docutils.sourceforge.net/docs/user/config.html
 
 [general]
-halt_level: severe
+halt_level: severe
\ No newline at end of file