Drop parse error for missing </caption> end tag

See https://html.spec.whatwg.org/multipage/parsing.html#parsing-main-incaption:stack-of-open-elements-2
The parse error for this case was dropped from the spec in
whatwg/html@759ee62

Relates to validator/validator#593
and https://bugzilla.mozilla.org/show_bug.cgi?id=1429415

Author: sideshowbarker

src/nu/validator/htmlparser/impl/TreeBuilder.java

@@ -1800,9 +1800,10 @@ public final void startTag(ElementName elementName,
                         case TBODY_OR_THEAD_OR_TFOOT:
                         case TR:
                         case TD_OR_TH:
-                            errStrayStartTag(name);
                             eltPos = findLastInTableScope("caption");
                             if (eltPos == TreeBuilder.NOT_FOUND_ON_STACK) {
+                                assert fragment || isTemplateContents();
+                                errStrayStartTag(name);
                                 break starttagloop;
                             }
                             generateImpliedEndTags();
@@ -3275,9 +3276,11 @@ public final void endTag(ElementName elementName) throws SAXException {
                             mode = IN_TABLE;
                             break endtagloop;
                         case TABLE:
-                            errTableClosedWhileCaptionOpen();
                             eltPos = findLastInTableScope("caption");
+
                             if (eltPos == TreeBuilder.NOT_FOUND_ON_STACK) {
+                                assert fragment || isTemplateContents();
+                                errStrayEndTag(name);
                                 break endtagloop;
                             }
                             generateImpliedEndTags();
@@ -6433,10 +6436,6 @@ private void errHtmlStartTagInForeignContext(@Local String name)
                 + "\u201D in a foreign namespace context.");
     }
 
-    private void errTableClosedWhileCaptionOpen() throws SAXException {
-        err("\u201Ctable\u201D closed but \u201Ccaption\u201D was still open.");
-    }
-
     private void errNoTableRowToClose() throws SAXException {
         err("No table row to close.");
     }