message: clarify Workers KV upgrade error
diff: @@ -77,7 +77,7 @@ fn help(error_code: u16) -> &'static str {
  // legacy namespace errors
  10021 | 10035 | 10038 => "Consider moving this namespace",
  // cloudflare account errors
  - 10017 | 10026 => "Workers KV is only available on the Workers Unlimited plan, please upgrade your account to use",
  + 10017 | 10026 => "Workers KV is a paid feature, please upgrade your account (https://www.cloudflare.com/products/workers-kv/)",
  _ => "",
  }
  }
  