GroupHeroBlock doesn't have cache context by user group permission

Problem/Motivation

GroupHeroBlock doesn't have cache context by the user group permissons, and when the group admin adds any member to the group with "Group members only (secret)" visibility this block doesn't appear for this member.

Steps to reproduce

1. Create a group with "Group members only (secret)" visibility
2. Create a user "Verified" with verified role
3. Go to the "About" page of the created group as a "Verified" user, and you should see "Access denied"
4. As a Site manager or Group Admin add a member - "Verified" user
5. Go to the "About" page of the created group as a "Verified" user, you will see group page but without GroupHeroBlock block
6. Flash cache - the GroupHeroBlock block will appear

Proposed resolution

Add cache context by user for GroupHeroBlock block:

/**
   * {@inheritDoc}
   */
  public function getCacheContexts(): array {
    return Cache::mergeContexts(parent::getCacheContexts(), [
      'user.group_permissions'
    ]);
  }