docs/qemu-option-trace.rst.inc: Remove redundant comment

The Texinfo version of the tracing options documentation has now
been deleted, so we can remove the now-redundant comment at the top
of the rST version that was reminding us that the two should be
kept in sync.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200306171749.10756-8-peter.maydell@linaro.org

docs/qemu-option-trace.rst.inc

@@ -1,7 +1,3 @@
-..
-  The contents of this file must be kept in sync with qemu-option-trace.texi
-  until all the users of the texi file have been converted to rst and
-  the texi file can be removed.
 
 Specify tracing options.