Fix height management in nuxeo-selectivity

Steps to reproduce:

1. add to nuxeo-note-create-layout.html after the description in a nuxeo-textarea element

         <nuxeo-document-suggestion role="widget"
                                    selectedItem = "selectedItem"
                                    value="{{document.properties.dc:language}}"
                                    label="Doc lie"
                                    required="true"
                                    selection-formatter="{{_selectionFormatter_objContact}}">
         </nuxeo-document-suggestion> 

2. add to the javascript part the code for selection formatter

       _selectionFormatter_objContact(doc)  {            
         var texte = '<iron-icon src="/nuxeo' + doc.properties['common:icon'] + '" class="avatar"></iron-icon>'  + doc.title;
         return texte;
       },
   

3. Go to the creation form of a Note
4. select one document by hitting "work" in the suggestion field
5. observe that the text for the selected item exceeds by the bottom of the input : it corresponds to the attached screenshot

With a higher value for .selectivity-single-select min-height, the display is correct/better : see More

I also attach the default behavior where the text does not exceed : see