Remove deprecated Staticman v1 config

Close #2386

_config.yml

@@ -43,23 +43,9 @@ comments:
   utterances:
     theme                : # "github-light" (default), "github-dark"
     issue_term           : # "pathname" (default)
-staticman:
-  allowedFields          : # ['name', 'email', 'url', 'message']
-  branch                 : # "master"
-  commitMessage          : # "New comment by {fields.name}"
-  filename               : # comment-{@timestamp}
-  format                 : # "yml"
-  moderation             : # true
-  path                   : # "/_data/comments/{options.slug}" (default)
-  requiredFields         : # ['name', 'email', 'message']
-  transforms:
-    email                : # "md5"
-  generatedFields:
-    date:
-      type               : # "date"
-      options:
-        format           : # "iso8601" (default), "timestamp-seconds", "timestamp-milliseconds"
-  endpoint               : # URL of your own deployment with trailing slash, will fallback to the public instance
+  staticman:
+    branch               : # "master"
+    endpoint             : # "https://{your Staticman v3 API}/v3/entry/github/"
 reCaptcha:
   siteKey                :
   secret                 :