chore(sops): Update encryption regex

Add externalName to encrypt internal DNS names. They might not be secret
but also of no value for people to read.

.sops.yaml

 creation_rules:
   - path_regex: (clusters|apps)/k8s01/.*.yaml
-    encrypted_regex: ^(data|stringData|email|dnsZones?|dnsNames?|.*(H|h)osts?|tang|externalURL|.*-secret|.*-url|.*Secrets?|.*-domain|password|subjects|node|apiURL|.*(S|s)erverNames?|.*SecretKey)$
+    encrypted_regex: ^(data|stringData|email|dnsZones?|dnsNames?|.*(H|h)osts?|tang|externalURL|.*-secret|.*-url|.*Secrets?|.*-domain|password|subjects|node|apiURL|.*(S|s)erverNames?|.*SecretKey|externalName)$
     pgp: >-
       286791FB6648539775DB31B8FCB98C2A3EC6F601,
       B137EE1549DFAF960DD1E2B15147025FB9F09E07