Editor: Forbid Jedi 0.9 as accepted version

Fixes #2659

This version is generating hard crashes for Spyder when introspecting
DataFrames, as it was reported in the mentioned issue.

spyderlib/utils/introspection/jedi_plugin.py

@@ -27,7 +27,7 @@
     jedi = None
 
 
-JEDI_REQVER = '>=0.8.1'
+JEDI_REQVER = '>=0.8.1;<0.9.0'
 dependencies.add('jedi',
                  _("(Experimental) Editor's code completion,"
                    " go-to-definition and help"),