Improve legibility of account/hashtag autosuggest (#31361)

app/javascript/styles/mastodon-light/diff.scss

@@ -559,3 +559,9 @@ a.sparkline {
 .report-dialog-modal__textarea {
   background: darken($ui-base-color, 10%);
 }
+
+.autosuggest-account {
+  .display-name__account {
+    color: $dark-text-color;
+  }
+}