docs: terraform state show is not machine-readable

In earlier versions of Terraform the result of terraform state show was
in the pre-0.12 "flatmap" structure that was unable to reflect nested
data structures. That was fixed in Terraform 0.12, but as a consequence
this statement about the output being machine-parseable (which was
debateable even in older versions) is incorrect.

Fortunately, we now have "terraform show -json" to get output that is
intentionally machine-parseable, so we'll recommend to use that instead
here. The JSON output of that command is a superset of what's produced by
"terraform state show", so should be usable to meet any use-case that
might previously have been met by parsing the "terraform state show"
output.

website/docs/commands/state/show.html.md

@@ -19,10 +19,6 @@ Usage: `terraform state show [options] ADDRESS`
 The command will show the attributes of a single resource in the
 state file that matches the given address.
 
-The attributes are listed in alphabetical order (with the except of "id"
-which is always at the top). They are outputted in a way that is easy
-to parse on the command-line.
-
 This command requires an address that points to a single resource in the
 state. Addresses are
 in [resource addressing format](/docs/commands/state/addressing.html).
@@ -32,6 +28,11 @@ The command-line flags are all optional. The list of available flags are:
 * `-state=path` - Path to the state file. Defaults to "terraform.tfstate".
   Ignored when [remote state](/docs/state/remote.html) is used.
 
+The output of `terraform state show` is intended for human consumption, not
+programmatic consumption. To extract state data for use in other software, use
+[`terraform show -json`](../show.html#json-output) and decode the result
+using the documented structure.
+
 ## Example: Show a Resource
 
 The example below shows a `packet_device` resource named `worker`: