Remove default from data properties

It looks like default is not supported in this version of the style
spec, so pending the PR to update it I'm removing it as an input.

src/components/fields/ZoomSpecField.jsx

@@ -190,20 +190,6 @@ export default class ZoomSpecProperty  extends React.Component {
             />
           </div>
         </div>
-        <div className="maputnik-data-spec-property-group">
-          <DocLabel
-            label="Default"
-            doc={"Input a default value for data if not covered by the scales."}
-          />
-          <div className="maputnik-data-spec-property-input">
-            <SpecField
-              fieldName={this.props.fieldName}
-              fieldSpec={this.props.fieldSpec}
-              value={this.props.value.default}
-              onChange={(_, newValue) => this.changeStop(idx, { zoom: zoomLevel, value: dataLevel }, newValue)}
-            />
-          </div>
-        </div>
       </InputBlock>
     </div>
       {dataFields}