Merge pull request #1344 from powdercloud/remove-html-legacy

remove legacy support for top level html (by @powdercloud)

validator/testdata/feature_tests/dog_doc_type.out

@@ -1,3 +1,4 @@
 FAIL
 feature_tests/dog_doc_type.html:23:0 DISALLOWED_ATTR 🐶
+feature_tests/dog_doc_type.html:24:0 MANDATORY_ATTR_MISSING ⚡ (see https://github.com/ampproject/amphtml/blob/master/spec/amp-html-format.md#ampd)
 feature_tests/dog_doc_type.html:35:7 MANDATORY_TAG_MISSING html ⚡ for top-level html (see https://github.com/ampproject/amphtml/blob/master/spec/amp-html-format.md#ampd)

validator/validator.protoascii

@@ -25,7 +25,7 @@ min_validator_revision_required: 70
 # newer versions of the spec file. This is currently a Google internal
 # mechanism, validator.js does not use this facility. However, any
 # change to this file requires updating this revision id.
-spec_file_revision: 105
+spec_file_revision: 106
 # Rules for AMP HTML
 # (https://github.com/google/amphtml/blob/master/spec/amp-html-format.md).
 # These rules are just enough to validate the example from the spec.
@@ -68,13 +68,6 @@ tags: {
     alternative_names: "amp"
   }
 }
-# Legacy support for when the amp identification is done by doctype.
-tags: {
-  name: "html"
-  detail: "top-level html"
-  mandatory_parent: "!doctype"
-  unique: true
-}
 # 4.2 Document metadata
 # 4.2.1 The head element
 tags: {