Fix external-dns PTR flag (--create-ptr) (#294)

external-dns v0.21.0 rejects --rfc2136-create-ptr (my error in #292) and the pod is crash-looping on flag parsing. The correct flag in this version is the generic --create-ptr, which synthesizes PTRs for A records whose reverse zone is in the domain filter (200.18.198.in-addr.arpa already is).

- Replaces --rfc2136-create-ptr with --create-ptr

Record reconciliation is stalled until this merges (serving unaffected — bind answers normally). MERGE ASAP.

Reviewed-on: #294
Co-authored-by: Ben Vincent <ben@unkin.net>
Co-committed-by: Ben Vincent <ben@unkin.net>

apps/overlays/au-syd1/externaldns/values.yaml

@@ -51,7 +51,7 @@ extraArgs:
   # Synthesize PTR records into the reverse zone for every A record managed in
   # the forward zone (the reverse zone + resolver forwarder exist since #288;
   # without this flag nothing writes PTRs).
-  - --rfc2136-create-ptr
+  - --create-ptr
   - --rfc2136-tsig-keyname=externaldns-key
   - --rfc2136-tsig-secret-alg=$(EXTERNAL_DNS_RFC2136_TSIG_ALGORITHM)
   - --rfc2136-tsig-axfr