Update digitalocean.html.markdown

separate v1 and v2 api

website/source/docs/builders/digitalocean.html.markdown

@@ -22,7 +22,7 @@ There are many configuration options available for the builder. They are
 segmented below into two categories: required and optional parameters. Within
 each category, the available configuration keys are alphabetized.
 
-### Required:
+### Required v1 api:
 
 * `api_key` (string) - The API key to use to access your account. You can
   retrieve this on the "API" page visible after logging into your account
@@ -36,6 +36,8 @@ each category, the available configuration keys are alphabetized.
   If not specified, Packer will use the environment variable
   `DIGITALOCEAN_CLIENT_ID`, if set.
 
+### Required v2 api:
+
 * `api_token` (string) - The client TOKEN to use to access your account. If it
   specified, then use v2 api (current), if not then used old (v1) deprecated api.
   Also it can be specified via environment variable `DIGITALOCEAN_API_TOKEN`, if set.