Change extensions/v1beta to apps/v1 to be compliant with Kubernetes 1.16

Fixes #1237

docs/kubernetes/mailu/admin.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-admin

docs/kubernetes/mailu/fetchmail.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-fetchmail

docs/kubernetes/mailu/imap.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-imap

docs/kubernetes/mailu/ingress.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Ingress
 metadata:
   name: mailu-ingress

docs/kubernetes/mailu/redis.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-redis

docs/kubernetes/mailu/security.yaml

@@ -1,5 +1,4 @@
-
+apiVersion: apps/v1
-apiVersion: extensions/v1beta1
 kind: Deployment
 metadata:
   name: mailu-security

docs/kubernetes/mailu/smtp.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-smtp

docs/kubernetes/mailu/webdav.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: mailu-webdav

docs/kubernetes/mailu/webmail.yaml

@@ -1,5 +1,4 @@
-
+apiVersion: apps/v1
-apiVersion: extensions/v1beta1
 kind: Deployment
 metadata:
   name: mailu-roundcube

docs/kubernetes/nginx/default-http-backend.yaml

@@ -1,4 +1,4 @@
-apiVersion: extensions/v1beta1
+apiVersion: apps/v1
 kind: Deployment
 metadata:
   name: default-http-backend