kubeadm: update the reference documentation for 1.15 (#14596)

* kubeadm-ref: update placeholder generated files

* kubeadm-ref: include reset-phase.md document

Also update reset.md to reflect the addition of reset phases.

* kubeadm-ref: update authored content

* kubeadm-ref: remove imports for removed "config upload" commands

* kubeadm-ref: add page for kubeadm upgrade phases

content/en/docs/reference/setup-tools/kubeadm/generated/kubeadm.md

@@ -5,7 +5,6 @@ kubeadm: easily bootstrap a secure Kubernetes cluster
 
 
 
-
     ┌──────────────────────────────────────────────────────────┐
     │ KUBEADM                                                  │
     │ Easily bootstrap a secure Kubernetes cluster             │
@@ -38,29 +37,8 @@ Example usage:
 
 ### Options
 
-<table style="width: 100%; table-layout: fixed;">
-  <colgroup>
-    <col span="1" style="width: 10px;" />
-    <col span="1" />
-  </colgroup>
-  <tbody>
-
-    <tr>
-      <td colspan="2">-h, --help</td>
-    </tr>
-    <tr>
-      <td></td><td style="line-height: 130%; word-wrap: break-word;">help for kubeadm</td>
-    </tr>
-
-    <tr>
-      <td colspan="2">--rootfs string</td>
-    </tr>
-    <tr>
-      <td></td><td style="line-height: 130%; word-wrap: break-word;">[EXPERIMENTAL] The path to the 'real' host root filesystem.</td>
-    </tr>
-
-  </tbody>
-</table>
-
-
+```
+  -h, --help            help for kubeadm
+      --rootfs string   [EXPERIMENTAL] The path to the 'real' host root filesystem.
+```