dedent yaml code blocks

otherwise extra redundant ````yaml` characters will be displayed
because github code fencing doesn't need any indentation

docs/admin/kubeadm.md

@@ -180,10 +180,10 @@ available as configuration file options.
 
 ### Sample Master Configuration
 
-    ```yaml
-    apiVersion: kubeadm.k8s.io/v1alpha1
-    kind: MasterConfiguration
-    api:
+```yaml
+apiVersion: kubeadm.k8s.io/v1alpha1
+kind: MasterConfiguration
+api:
   advertiseAddresses:
   - <address1|string>
   - <address2|string>
@@ -191,38 +191,38 @@ available as configuration file options.
   externalDNSNames:
   - <dnsname1|string>
   - <dnsname2|string>
-    authorizationMode: <string>
-    cloudProvider: <string>
-    discovery:
+authorizationMode: <string>
+cloudProvider: <string>
+discovery:
   bindPort: <int>
-    etcd:
+etcd:
   endpoints:
   - <endpoint1|string>
   - <endpoint2|string>
   caFile: <path|string>
   certFile: <path|string>
   keyFile: <path|string>
-    kubernetesVersion: <string>
-    networking:
+kubernetesVersion: <string>
+networking:
   dnsDomain: <string>
   serviceSubnet: <cidr>
   podSubnet: <cidr>
-    secrets:
+secrets:
   givenToken: <token|string>
-    ```
+```
 
 ### Sample Node Configuration
 
-    ```yaml
-    apiVersion: kubeadm.k8s.io/v1alpha1
-    kind: NodeConfiguration
-    apiPort: <int>
-    discoveryPort: <int>
-    masterAddresses:
-    - <master1>
-    secrets:
+```yaml
+apiVersion: kubeadm.k8s.io/v1alpha1
+kind: NodeConfiguration
+apiPort: <int>
+discoveryPort: <int>
+masterAddresses:
+- <master1>
+secrets:
   givenToken: <token|string>
-    ```
+```
 
 ## Automating kubeadm