scraper: pass values to In as a set instead of individually

The function signature is `In(container, msg=None)`, so
`ipv4Prefix` is being considered the single value in the
container, and `ipv6Prefix` is being mapped to `msg`.

scripts/scrape-manifest-ip-ranges.py

@@ -268,7 +268,7 @@ def get_gcp_ips():
             'prefixes': All(all_required_gcp_regions_exist, [
                 {
                     # One of these tags must be present, and it's value must be an IP block.
-                    In('ipv4Prefix', 'ipv6Prefix'): is_ip_address_network,
+                    In({'ipv4Prefix', 'ipv6Prefix'}): is_ip_address_network,
                     'scope': str,
                     'service': str,
                 },