Change the text-danger color to increase the contrast

The issue only affects one theme: High Contrast Dark

Signed-off-by: RD WebDesign <github@rdwebdesign.com.br>

style/themes/high-contrast-dark.css

@@ -483,6 +483,11 @@ kbd {
   color: #808890;
 }
 
+/* Used in error403 */
+.text-danger {
+  color: #f54;
+}
+
 .warning-count {
   color: #000;
   background: #f94;