Use `Icon` in `ShareAnnotationsPanel`

src/sidebar/components/ShareAnnotationsPanel.js

 import {
   IconButton,
   Spinner,
-  SvgIcon,
+  Icon,
   TextInput,
   TextInputWithButton,
 } from '@hypothesis/frontend-shared';
@@ -105,8 +105,8 @@ function ShareAnnotationsPanel({ toastMessenger }) {
                 )}{' '}
                 <span>
                   Private (
-                  <SvgIcon name="lock" inline className="u-icon--inline" />{' '}
-                  <em>Only Me</em>) annotations are only visible to you.
+                  <Icon name="lock" classes="u-inline" /> <em>Only Me</em>)
+                  annotations are only visible to you.
                 </span>
               </p>
               <ShareLinks shareURI={shareURI} />