fix: use backticks in audit

Co-authored-by: Mike McQuaid <[email protected]>

Library/Homebrew/formula_auditor.rb

@@ -596,20 +596,20 @@ def audit_wayback_url
 
  regex = %r{^https?://web\.archive\.org}
  if regex.match?(formula.stable.url)
- problem "Formula with a Wayback URL should be deprecated with `:repo_removed`"
+ problem "Formula with a Wayback Machine `url` should be deprecated with `:repo_removed`"
  return
  end
 
  if regex.match?(formula.homepage)
- problem "Formula with a Wayback homepage should find an alternative homepage"
+ problem "Formula with a Wayback Machine `homepage` should find an alternative `homepage`"
  return
  end
 
  return unless formula.head
 
  return unless regex.match?(formula.head.url)
 
- problem "Formula with a Wayback `HEAD` URL should not have a `HEAD` definition"
+ problem "Formula with a Wayback `head` should not have a `head` definition"
  end
 
  def audit_github_repository_archived