change btn color to not see-through

src/client/js/components/SearchPage/SearchPageForm.jsx

@@ -42,7 +42,7 @@ class SearchPageForm extends React.Component {
           />
         </div>
         <div className="input-group-append">
-          <button className="btn btn-outline-secondary" type="button" id="button-addon2" onClick={this.search}>
+          <button className="btn btn-secondary" type="button" id="button-addon2" onClick={this.search}>
             <i className="icon-magnifier"></i>
           </button>
         </div>