Fix expansion of toolbar in the exam environment

Currently, the exam environment includes an old version of
rich-text-editor, which overrides much of our style changes. As a
workaround, rename the rich-text-editor-characters-expanded class so our
changes to it won't be overridden.

public/rich-text-editor.css

@@ -167,7 +167,7 @@
   transition: top 0.15s;
 }
 
-.rich-text-editor-focus .rich-text-editor-characters-expanded {
+.rich-text-editor-focus .rich-text-editor-show-all-characters {
   top: 0;
 }
 
@@ -255,7 +255,7 @@
   display: none;
 }
 
-.rich-text-editor-characters-expanded .rich-text-editor-toolbar-characters .rich-text-editor-button,
+.rich-text-editor-show-all-characters .rich-text-editor-toolbar-characters .rich-text-editor-button,
 .rich-text-editor-toolbar-characters .rich-text-editor-button.rich-text-editor-characters-popular {
   display: inline-block;
 }
@@ -276,7 +276,7 @@
   background: url('expand.svg') 50% 50% no-repeat;
 }
 
-.rich-text-editor-characters-expanded .rich-text-editor-characters-expand-collapse {
+.rich-text-editor-show-all-characters .rich-text-editor-characters-expand-collapse {
   background-image: url('collapse.svg');
 }
 

src/toolbars.js

@@ -67,7 +67,7 @@ export function init(mathEditor, hasRichTextFocus, l, baseUrl) {
         })
         .on('mousedown', '[data-js="expandCollapseCharacters"]', (e) => {
             e.preventDefault()
-            $toolbar.toggleClass('rich-text-editor-characters-expanded')
+            $toolbar.toggleClass('rich-text-editor-show-all-characters')
         })
         .on('mousedown', '[data-js="richTextEditorHelp"]', (e) => {
             e.preventDefault()