Add !default to $max-height in popup.scss

[davidrojo]

In popup.scss, the variable $max-height doesn't have the !default, which prevents it to be overwrited via custom variables.

So without the !default i cannot do this:

@use "~react-widgets/scss/styles.scss" with (
  $widget-border-radius: $input-border-radius,
  $widget-border-color: $input-border-color,
  $widget-focus-box-shadow: $input-focus-box-shadow,
  $max-height: 400px
);

As I get the following error:

Module build failed (from ./node_modules/mini-css-extract-plugin/dist/loader.js):
ModuleBuildError: Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: This variable was not declared with !default in the @used module.
  ╷
5 │   $max-height: 400px
  │   ^^^^^^^^^^^^^^^^^^
  ╵