Remove antiquated kube-lego references

[kube-lego](https://github.com/jetstack/kube-lego) was the
precursor to cert-manager, and has been dead for years and
years now

helm-chart/binderhub/schema.yaml

@@ -519,10 +519,6 @@ properties:
             type: boolean
             description: |
               TODO
-          type:
-            type: string
-            description: |
-              TODO
       annotations:
         type: object
         additionalProperties: false

helm-chart/binderhub/templates/ingress.yaml

@@ -3,12 +3,8 @@ apiVersion: networking.k8s.io/v1
 kind: Ingress
 metadata:
   name: binderhub
-  {{- if or (and .Values.ingress.https.enabled (eq .Values.ingress.https.type "kube-lego")) .Values.ingress.annotations }}
+  {{- with .Values.ingress.annotations }}
   annotations:
-    {{- if and .Values.ingress.https.enabled (eq .Values.ingress.https.type "kube-lego") }}
-    kubernetes.io/tls-acme: "true"
-    {{- end }}
-    {{- with .Values.ingress.annotations }}
     {{- . | toYaml | nindent 4 }}
     {{- end }}
   {{- end }}
@@ -31,14 +27,7 @@ spec:
       host: {{ . | quote }}
       {{- end }}
     {{- end }}
-  {{- if and .Values.ingress.https.enabled (eq .Values.ingress.https.type "kube-lego") }}
-  tls:
-    - secretName: kubelego-tls-binder-{{ .Release.Name }}
-      hosts:
-        {{- range .Values.ingress.hosts }}
-        - {{ . | quote }}
-        {{- end }}
-  {{- else if .Values.ingress.tls }}
+  {{- if .Values.ingress.tls }}
   tls:
     {{- range .Values.ingress.tls }}
     - hosts: