[doc] Notice deprecated old color format

Change-Id: I87c61a08a696b7330ddc9f5464322f19469a15fe

ROADMAP.rst

@@ -119,6 +119,7 @@ Will be removed in Pywikibot 10
 * 7.6.0: :mod:`tools.collections` datatypes should no longer imported from :mod:`tools`
 * 7.5.0: :mod:`textlib`.tzoneFixedOffset class will be removed in favour of :class:`time.TZoneFixedOffset`
 * 7.4.0: ``FilePage.usingPages()`` was renamed to :meth:`using_pages()<pywikibot.FilePage.using_pages>`
+* 7.3.0: Old color escape sequences like ``\03{color}`` is deprecated in favour of new color format like <<color>>
 * 7.3.0: ``linkitrail`` method of :class:`family.Family` is deprecated; use :meth:`APISite.linktrail()
   <pywikibot.site._apisite.APISite.linktrail>` instead
 * 7.2.0: ``tb`` parameter of :func:`exception()<pywikibot.exception>` function was renamed to ``exc_info``