fix(html): fix AST_COMPARE on htmlparser2 ASTs (#2084)

src/clean-ast.js

@@ -51,7 +51,9 @@ function massageAST(ast) {
       "source",
       "before",
       "after",
-      "trailingComma"
+      "trailingComma",
+      "parent",
+      "prev"
     ].forEach(name => {
       delete newObj[name];
     });

tests_config/run_spec.js

@@ -96,7 +96,9 @@ function stripLocation(ast) {
         key === "loc" ||
         key === "range" ||
         key === "raw" ||
-        key === "comments"
+        key === "comments" ||
+        key === "parent" ||
+        key === "prev"
       ) {
         continue;
       }