Fix jason edit mac (#1791)

* Condition wx.SetExtraStyle on MacOS

* Remove not needed style in JSON Editor

Author: HelioGuilherme66

src/robotide/editor/kweditor.py

@@ -788,7 +788,6 @@ def OnJsonEditor(self, event=None):
             event.Skip()
         dialog = Dialog()
         dialog.SetTitle('JSON Editor')
-        dialog.SetExtraStyle(wx.RESIZE_BORDER)
         dialog.SetSizer(wx.BoxSizer(wx.HORIZONTAL))
         okBtn = wx.Button(dialog, wx.ID_OK, "Save")
         cnlBtn = wx.Button(dialog, wx.ID_CANCEL, "Cancel")