Update advanced search language

Why these changes are being introduced:

UXWS has requested that he simplify the language for the
advanced search dropdown.

Relevant ticket(s):

* https://mitlibraries.atlassian.net/browse/GDT-126

How this addresses that need:

This updates the language as requested: "Advanced search" when the
dropdown is closed, and "Close advanced search" when it's open.

Side effects of this change:

Though it emerged from the GDT UI design work, this is a general
enhancement that will apply to all TIMDEX UI apps.

Author: jazairi

app/javascript/search_form.js

@@ -6,15 +6,15 @@ function disableAdvanced() {
   );
   keyword_field.setAttribute('placeholder', 'Enter your search');
   advanced_label.classList = 'closed';
-  advanced_label.innerText = 'Show advanced search fields';
+  advanced_label.innerText = 'Advanced search';
 };
 
 function enableAdvanced() {
   advanced_field.setAttribute('value', 'true');
   keyword_field.setAttribute('aria-required', false);
   keyword_field.setAttribute('placeholder', 'Keyword anywhere');
   advanced_label.classList = 'open';
-  advanced_label.innerText = 'Clear advanced search fields';
+  advanced_label.innerText = 'Close advanced search';
 };
 
 var advanced_field = document.getElementById('advanced-search-field');

app/views/search/_form.html.erb

@@ -6,11 +6,11 @@ if params[:q]
 end
 
 # Initial form setup is determined by the advanced parameter. Thereafter it is altered by javascript.
-advanced_label = "Show advanced search fields"
+advanced_label = "Advanced search"
 advanced_label_class = "closed"
 search_required = true
 if params[:advanced] == "true"
-  advanced_label = "Clear advanced search fields"
+  advanced_label = "Close advanced search"
   advanced_label_class = "open"
   search_required = false
 end