[es7] Prepare support for elasticsearch 7.0.0

cubicweb_elasticsearch/__pkginfo__.py

@@ -15,8 +15,8 @@
 
 __depends__ = {'cubicweb': '>= 3.24.0', 'six': '>= 1.4.0',
                'cwtags': None,
-               'elasticsearch': '>=6.0.0,<7.0.0',
-               'elasticsearch-dsl': '>=6.0.0,<7.0.0',
+               'elasticsearch': '>=7.0.0,<8.0.0',
+               'elasticsearch-dsl': '>=7.0.0,<8.0.0',
                'beautifulsoup4': None,
                }