message: fix(CustomSelectDropdown): fix token for background
diff: .CustomSelectDropdown {
  overflow: hidden;
  - background-color: var(--vkui--color_background_content);
  + background-color: var(--vkui--color_background_modal);
  box-sizing: border-box;
  border: var(--thin-border) solid var(--vkui--color_separator_primary_alpha);
  box-shadow: var(--vkui--elevation1);
  