Remove zformat from hoverlabels layout properties

Author: jdugge

src/components/fx/layout_attributes.js

@@ -72,17 +72,6 @@ module.exports = {
                 '`namelength - 3` characters and add an ellipsis.'
             ].join(' ')
         },
-        zformat: {
-            valType: 'string',
-            dflt: '',
-            role: 'style',
-            editType: 'none',
-            description: [
-                'Sets the hover text formatting rule using d3 formatting mini-languages',
-                'which are very similar to those in Python. See:',
-                'https://github.com/d3/d3-format/blob/master/README.md#locale_format'
-            ].join(' ')
-        },
         editType: 'none'
     }
 };