Update configuration of the website repo

[Kobzol]

After the change of the website to a static web, we:

• Should not need the deploy branch protection
• We should require PRs for the main branch (IMO), as it is now automatically deployed
• The website team should not need maintain permissions anymore, as Pontoon is no longer used
• We don't need the Heroku bot anymore

CC @senekor if this looks good.

[github-actions]

Dry-run check results

[WARN  sync_team] sync-team is running in dry mode, no changes will be applied.
[INFO  sync_team] synchronizing github
[INFO  sync_team] 💻 Repo Diffs:
    📝 Editing repo 'rust-lang/www.rust-lang.org':
      Permission Changes:
        Changing team 'website''s permission from maintain to write
        Removing user 'rust-heroku-deploy-access''s admin permission 
      Branch Protections:
          main
            Required Approving Review Count: 0 => 1
            Requires PR: false => true
          deploy
            Deleting branch protection

[Kobzol]

Rebased.