Recommend removing extra metadata

Add wording that recommends removing extra metadata from machine templates retrieved from a working cluster before re-applying them

Signed-off-by: Scott Lowe <[email protected]>

docs/book/src/tasks/change-machine-template.md

@@ -17,7 +17,10 @@ The correct process for modifying an infrastructure machine template is as follo
     for more details on the specific fields that each provider requires or accepts.
 3. Give the newly-modified template a new name by modifying the `metadata.name` field 
     (or by using `metadata.generateName`).
-4. Create the new infrastructure machine template on the API server using `kubectl`.
+4. Create the new infrastructure machine template on the API server using `kubectl`. 
+    (If the template was initially created using the command in step 1, be sure to clear 
+    out any extraneous metadata, including the `resourceVersion` field, before trying to 
+    send it to the API server.)
 
 Once the new infrastructure machine template has been persisted, users may modify 
 the object that was referencing the infrastructure machine template. For example,