Exclude tags from collection.liquid filter when using tags to show related prodcuts

shopify-remove-relatedtags.liquid

{% comment %}
Based on using Tags to show related products. 
Credit : http://twigs.club/library/hand-picked-related-products-using-tags-or-metafields
{% endcomment %}

<div class="collection-sort">
  <label for="SortBy" class="collection-sort__label">{{ 'collections.sorting.title_tags' | t }}</label>
    <select name="SortTags" id="SortTags" class="collection-sort__input">
      {% if collection.handle %}
        <option value="/collections/{{ collection.handle }}">{{ 'collections.sorting.all_of_collection' | t: collection: collection.title }}</option>
      {% elsif collection.current_type %}
        <option value="{{ collection.current_type | url_for_type }}">{{ 'collections.sorting.all_of_collection' | t: collection: collection.title }}</option>
      {% elsif collection.current_vendor %}
        <option value="{{ collection.current_vendor | url_for_vendor }}">{{ 'collections.sorting.all_of_collection' | t: collection: collection.title }}</option>
      {% endif %}

      {% comment %}
        Show all tags on the current collection of products and hide any that contain related-
      {% endcomment %}
            
      {% for tag in collection.all_tags %}
        {% if tag contains 'related-' %} {% comment %} DO NOTHING {% endcomment %}
        {% else %}
          <option value="/collections/{% if collection.handle != blank %}{{ collection.handle }}{% else %}all{% endif %}/{{ tag | handleize }}"{% if current_tags contains tag %} selected="selected"{% endif %}>{{ tag }}</option>
        {% endif %}
      {% endfor %}
    </select>
</div>