Update Helm release external-dns/external-dns to v1.21.1 (#1805)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

examples/external_dns.yaml

@@ -11,7 +11,7 @@ spec:
   - repositoryURL:    https://kubernetes-sigs.github.io/external-dns/
     repositoryName:   external-dns
     chartName:        external-dns/external-dns
-    chartVersion:     1.20.0
+    chartVersion:     1.21.1
     releaseName:      external-dns
     releaseNamespace: external-dns
     helmChartAction:  Install